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Explicit Main Idea

42 questions

All types42Multiple choice22True / False9Matching11
Question 1Question →

Match each technical passage describing military and aerospace engineering systems with the statement that expresses its explicitly stated main idea.

Click a left item, then click its matching right item

Items

Ultrasonic non-destructive inspection remains the most reliable method for detecting hidden subsurface delamination in aircraft composite structures. High-frequency acoustic waves pass into the carbon-fiber layers, reflecting back at different rates when internal voids or resin separations occur. Technicians monitor these echo patterns on diagnostic displays to evaluate material integrity without causing structural damage. Early discovery of these microscopic separations prevents catastrophic panel failure during high-stress flight maneuvers.
Tactical radio units maintain operational security in hostile electronic warfare environments through frequency-hopping spread spectrum technology. Rather than transmitting continuously along a single channel, the radio rapidly shifts carrier frequencies hundreds of times per second according to a pre-shared cryptographic key. This rapid frequency shifting makes military broadcasts exceptionally difficult for enemy systems to intercept or jam. Supporting transmitters synchronize their hopping sequences automatically, allowing continuous tactical voice traffic to proceed uninterrupted.
Submerged naval vessels rely primarily on water electrolysis units to maintain continuous breathable oxygen levels for the crew. These electrochemical generators split purified demineralized water into gaseous hydrogen and oxygen using electrical power from the onboard reactor. The generated hydrogen is safely vented overboard or converted, while the concentrated oxygen is metered directly into the submarine's ventilation system. Continuous automated sensors monitor cabin partial pressures to ensure the atmospheric balance remains safe during prolonged underwater deployments.

Matches

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Answer

Passage 1 matches with the statement on ultrasonic non-destructive testing identifying internal layer separations in aircraft structures; Passage 2 matches with the statement on frequency-hopping spread spectrum securing tactical radio communications against jamming; Passage 3 matches with the statement on electrolytic water-splitting generators serving as the primary oxygen source for submerged crews.
Each passage explicitly presents its central concept in an identifiable opening topic sentence. The first passage focuses on ultrasonic inspection as the premier method for uncovering hidden composite delamination; the second passage establishes frequency-hopping spread spectrum as the primary technology for securing tactical radio transmissions against jamming; and the third passage explicitly defines water electrolysis as the primary system supplying breathable oxygen to submerged submarine crews.

Step-by-Step Solution

1
Examine the first passage to locate its explicitly stated topic sentence.
The lead sentence states: 'Ultrasonic non-destructive inspection remains the most reliable method for detecting hidden subsurface delamination in aircraft composite structures.'
Explicit main ideas in technical passages are often located in the opening sentence, framing the entire discussion of acoustic wave reflections and integrity checks.
2
Examine the second passage to identify its central explicit assertion.
The lead sentence states: 'Tactical radio units maintain operational security in hostile electronic warfare environments through frequency-hopping spread spectrum technology.'
The supporting sentences elaborate on how frequency changes work and prevent jamming, reinforcing that the core claim is operational communication security via frequency hopping.
3
Examine the third passage to identify its explicit primary claim.
The lead sentence states: 'Submerged naval vessels rely primarily on water electrolysis units to maintain continuous breathable oxygen levels for the crew.'
Subsequent details describe electrochemical splitting and gas metering, which support the principal stated function of water electrolysis for oxygen generation.
4
Pair each technical passage with its corresponding paraphrased explicit main idea statement.
All three passages are paired accurately with their exact topic-level summaries.
Matching each explicit topic sentence ensures that central points are distinguished from specific supporting mechanisms.

Key Concept

Identifying explicitly stated main ideas in technical passages
Estimated Time:1m 30s
Question 2Question →

Hydraulic accumulators serve as critical energy storage devices that maintain essential system pressure in tactical vehicle hydraulic circuits. When the engine-driven hydraulic pump operates under normal conditions, excess fluid compresses a nitrogen gas bladder within the accumulator shell. If sudden steering demands exceed pump output or if the primary pump fails entirely, this compressed gas forces stored fluid back into the lines to power steering and braking actuators. While standard fluid reservoirs only hold unpressurized reserve oil, accumulators guarantee immediate high-pressure reserve power during critical mechanical emergencies.

Which of the following statements best expresses the main idea of the passage?

Show answer & explanation

Answer: Hydraulic accumulators store pressurized fluid to maintain necessary operational pressure in vehicle hydraulic systems.

Answer

Hydraulic accumulators store pressurized fluid to maintain necessary operational pressure in vehicle hydraulic systems.
The correct option captures the central topic explicitly introduced in the first sentence and developed throughout the paragraph: hydraulic accumulators act as energy storage components that maintain necessary hydraulic pressure.

Step-by-Step Solution

1
Read the passage and locate the explicit topic sentence.
The opening sentence directly states that hydraulic accumulators serve as critical energy storage devices maintaining essential system pressure in tactical vehicle hydraulic circuits.
Explicit main ideas in technical expository texts are typically stated directly in the lead or summary sentences.
2
Evaluate the remaining sentences to verify they function as supporting details.
Sentences 2, 3, and 4 explain how the accumulator charges, how it discharges under high demand or failure, and contrast it with unpressurized reservoirs.
Supporting details provide mechanisms and context that reinforce the primary claim without replacing it.
3
Match the core claim to the option that accurately paraphrases the entire passage's scope.
The statement expressing that hydraulic accumulators store pressurized fluid to maintain necessary operating pressure perfectly aligns with the explicit topic sentence.
The correct answer must encompass the entire passage rather than single steps or secondary comparisons.

Key Concept

Explicit Main Idea Identification
Estimated Time:1m 0s
Question 3Question →

Read the three technical field maintenance excerpts below regarding tactical engine systems. Match each passage to its explicitly stated main idea.

Click a left item, then click its matching right item

Items

Passage 1: Centrifugal oil spinners are essential for removing microscopic soot particles that bypass standard pleated filters in heavy diesel engines. While conventional cellulose filters trap larger metallic shavings and debris, fine carbon particulates under five microns circulate freely, causing gradual abrasive wear on bearing journals. The spinner uses rotational velocity powered by engine oil pressure to fling these microscopic contaminants against an outer removable canister, thereby preserving lubricant integrity and extending engine operational life.
Passage 2: Tactical vehicles operating in sub-zero environments rely on glow plugs to heat the engine combustion chambers prior to cranking. Extreme cold causes diesel fuel to atomize poorly and prevents the intake air charge from reaching the auto-ignition temperature during piston compression. By energizing a high-resistance heating element inside each cylinder head, glow plugs ensure rapid fuel ignition, reduce electrical starter motor strain, and prevent unburned fuel from washing protective oil off cylinder walls during winter missions.
Passage 3: Positive crankcase ventilation systems prevent dangerous internal pressure buildup and seal blowouts by continuously routing blow-by gases back into the engine intake manifold. During normal combustion, a fraction of high-pressure combustion vapor inevitably slips past the piston rings into the lower engine crankcase. Without a dedicated continuous pathway to evacuate these pressurized vapors, corrosive moisture condenses inside the oil pan and crankcase oil seals rupture under accumulated internal pressure.

Matches

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Answer

Passage 1 matches the statement regarding centrifugal oil spinners removing microscopic soot; Passage 2 matches the statement regarding glow plugs preheating combustion chambers in sub-zero conditions; Passage 3 matches the statement regarding positive crankcase ventilation systems rerouting blow-by gases to prevent seal failure.
Each passage features an explicit topic sentence at the very beginning that clearly defines the component's core operational purpose. The correct pairings directly align each passage's primary claim with its matching summary without drifting into narrow supporting details.

Step-by-Step Solution

1
Locate the explicit topic sentence in Passage 1.
The lead sentence states: 'Centrifugal oil spinners are essential for removing microscopic soot particles that bypass standard pleated filters in heavy diesel engines.'
Explicit main ideas in technical expository paragraphs are stated directly in topic sentences that define the primary mechanism and purpose of the passage.
2
Locate the explicit topic sentence in Passage 2.
The lead sentence states: 'Tactical vehicles operating in sub-zero environments rely on glow plugs to heat the engine combustion chambers prior to cranking.'
The entire paragraph elaborates on cold-weather ignition challenges, confirming the lead sentence as the overarching explicit claim.
3
Locate the explicit topic sentence in Passage 3.
The lead sentence states: 'Positive crankcase ventilation systems prevent dangerous internal pressure buildup and seal blowouts by continuously routing blow-by gases back into the engine intake manifold.'
The subsequent details explain why blow-by occurs and what happens without venting, supporting the primary thesis in the first sentence.

Key Concept

Identifying explicitly stated topic sentences that encapsulate the overall purpose and mechanics of technical expository paragraphs.
Estimated Time:1m 30s
Question 4Question →

Aviation fuel storage systems are highly vulnerable to biological degradation when microscopic fungi thrive in stagnant water pockets at tank bottoms. These microorganisms consume hydrocarbons, multiplying rapidly and generating corrosive acidic byproducts. Over time, thick fungal mats can clog fuel filters, corrode internal aluminum lines, and cause erratic fuel gauge readings. Consequently, routinely draining accumulated water from tank sumps is the most effective operational method for preventing microbial contamination in aviation fuel systems.

According to the passage, which of the following expresses the main idea?

Show answer & explanation

Answer: Routinely draining water from tank sumps is the most effective method to prevent microbial fuel contamination.

Answer

Routinely draining water from tank sumps is the most effective method to prevent microbial fuel contamination.
The passage builds up by explaining how microbial growth occurs in stagnant water and the damage it causes, culminating in the explicit topic sentence in the final line: 'Consequently, routinely draining accumulated water from tank sumps is the most effective operational method for preventing microbial contamination in aviation fuel systems.' The correct option directly reflects this explicit claim.

Step-by-Step Solution

1
Read the passage to identify the central topic and scope.
The text discusses how water causes fungal growth in aviation fuel tanks and concludes with the primary preventive measure.
Understanding the full context helps separate background facts from the core takeaway.
2
Locate the explicit topic sentence that unifies the paragraph.
The concluding sentence explicitly states: 'Consequently, routinely draining accumulated water from tank sumps is the most effective operational method for preventing microbial contamination in aviation fuel systems.'
Expository technical paragraphs often place the explicit main idea in the final sentence as a synthesis or conclusion.
3
Match the explicit statement to the corresponding answer choice.
The option stating that routinely draining water from tank sumps is the most effective method directly paraphrases the explicit topic sentence.
The correct response must capture the main idea rather than isolated supporting details or unstated exaggerations.

Key Concept

Explicit Main Idea Identification
Estimated Time:1m 0s
Question 5Question →

Proper tire pressure is critical for ensuring the safe operation and fuel efficiency of military transport vehicles. When tires are underinflated, the increased friction causes excessive heat buildup, which can lead to sudden tread separation and dangerous blowouts on rough terrain. Furthermore, low pressure increases rolling resistance, forcing the engine to consume significantly more fuel during long supply convoys. Routine pre-trip pressure checks prevent these mechanical hazards and reduce unnecessary fleet maintenance costs.

Which of the following best expresses the main idea of the passage?

Show answer & explanation

Answer: Maintaining correct tire pressure is essential for the safety and fuel performance of transport vehicles.

Answer

Maintaining correct tire pressure is essential for the safety and fuel performance of transport vehicles.
The correct response directly restates the explicitly stated topic sentence found at the beginning of the passage, summarizing both primary points: vehicle safety and fuel efficiency.

Step-by-Step Solution

1
Locate the explicit topic sentence in the paragraph.
The first sentence directly states: 'Proper tire pressure is critical for ensuring the safe operation and fuel efficiency of military transport vehicles.'
Explicit main ideas are directly stated within the text, frequently in the opening sentence.
2
Evaluate the subsequent sentences to verify they serve as supporting details.
The following sentences provide specific evidence: one explains the safety hazard (heat buildup and blowouts) and the next explains the efficiency impact (increased fuel consumption).
Confirming that remaining details develop the opening claim ensures the topic sentence is indeed the overarching main idea.
3
Match the core claim to the corresponding answer choice.
The statement expressing that maintaining correct tire pressure is essential for safety and fuel performance directly paraphrases the topic sentence.
The correct choice must capture the comprehensive main idea rather than an isolated detail or broad generalization.

Key Concept

Explicit Main Idea
Estimated Time:45s
Question 6Question →

In marine propulsion, cavitation develops when localized pressure drops in the fluid cause microscopic vapor bubbles to form and violently implode against moving components. While operators frequently identify cavitation by its distinctive acoustic signature and hull vibration, the primary operational hazard of cavitation is the severe physical erosion and surface pitting it inflicts on propeller blades over time. The concentrated energy released during bubble collapse continually strips protective coatings, degrades structural integrity, and alters hydrodynamic efficiency. Consequently, naval engineering protocols mandate strict operational speed limits and routine acoustic monitoring specifically to reduce the rate of this destructive surface wear.

Which of the following statements best expresses the main idea of the passage?

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Answer: Cavitation poses a major operational hazard primarily because it causes progressive physical erosion and structural damage to propeller blades.

Answer

Cavitation poses a major operational hazard primarily because it causes progressive physical erosion and structural damage to propeller blades.
The passage explicitly establishes that although acoustic signatures and vibrations are notable symptoms, the primary operational hazard of cavitation is the physical erosion and surface damage it inflicts on propeller blades. The correct option directly captures this explicitly stated main idea.

Step-by-Step Solution

1
Locate the explicit topic sentence containing the central assertion.
The second sentence explicitly states: 'the primary operational hazard of cavitation is the severe physical erosion and surface pitting it inflicts on propeller blades over time.'
Explicit main idea questions require finding the direct statement that governs the entire paragraph's purpose and scope.
2
Evaluate the remaining sentences to verify they serve as supporting context and consequences.
The acoustic signature is introduced as a diagnostic signal, the third sentence describes the mechanics of erosion, and the concluding sentence describes preventive procedures.
Distinguishing between the core thesis and supporting details prevents selecting narrow distractors.
3
Match the explicit claim to the corresponding option while eliminating scope distortions and detail traps.
The option emphasizing progressive physical erosion and structural damage directly reflects the explicit main idea.
The correct response accurately synthesizes the topic sentence without overgeneralizing or focusing solely on minor supporting details.

Key Concept

Identifying an explicitly stated topic sentence embedded within technical prose by separating the main operational claim from secondary symptoms and procedural responses.
Estimated Time:1m 15s
Question 7Question →

Read each short technical passage and match it to the statement that expresses its explicitly stated main idea.

Click a left item, then click its matching right item

Items

Radar operators on naval vessels must maintain continuous visual monitoring of display screens to ensure navigational safety. During night operations, surface clutter and atmospheric interference can obscure small vessels or floating obstacles. By constantly adjusting gain settings and tracking signal returns, operators identify potential collision hazards before they pose an immediate threat.
Standard pre-flight inspections are mandatory for military aircraft to prevent mechanical failure during flight. Ground crews systematically inspect control surfaces, hydraulic lines, and engine cowlings for loose fasteners or fluid leaks. Identifying and repairing minor component wear before takeoff eliminates operational hazards and guarantees mission readiness.
Wearing layered clothing is the most effective method for personnel to prevent hypothermia in Arctic environments. An inner synthetic layer wicks moisture away from the skin, while a middle insulating layer traps body heat. An outer windproof shell blocks freezing winds, allowing personnel to regulate warmth by adjusting individual garments as activity changes.

Matches

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Answer

Passage 1 matches 'Continuous radar screen monitoring is essential for maintaining naval vessel safety.', Passage 2 matches 'Mandatory pre-flight aircraft inspections prevent in-flight mechanical failures.', and Passage 3 matches 'Layered clothing is the most effective way to prevent hypothermia in Arctic environments.'
Each passage presents its main idea explicitly in the opening sentence. The first passage establishes that continuous radar monitoring ensures vessel safety; the second establishes that pre-flight inspections prevent in-flight mechanical failures; and the third establishes that wearing layered clothing is the most effective method to prevent hypothermia.

Step-by-Step Solution

1
Locate the explicit topic sentence in each paragraph.
Each paragraph opens with an explicit declarative sentence containing the overarching point: Passage 1 focuses on continuous radar monitoring for safety, Passage 2 focuses on mandatory pre-flight checks to prevent failures, and Passage 3 focuses on layered clothing to prevent hypothermia.
An explicit main idea is directly stated in the text, commonly found in the lead topic sentence of expository paragraphs.
2
Differentiate between the central thesis and supporting technical details.
Details such as wicking moisture, checking hydraulic lines, or adjusting gain settings serve to explain how the main idea operates rather than representing the complete message.
Supporting details reinforce the main idea but do not encompass the full scope of the passage.
3
Pair each passage with its exact corresponding main idea statement.
All three passages are paired accurately with their paraphrased topic sentences.
Matching each text to its primary claim verifies accurate comprehension of explicit main ideas.

Key Concept

Explicit Main Idea Identification
Estimated Time:1m 0s
Question 8Question →

Hydraulic fluid contamination is the primary cause of mechanical degradation and valve failure in modern aircraft flight control systems. Particulate matter entering hydraulic lines causes accelerated abrasion against precision-machined actuators, leading to fluid bypass and delayed control surface response. In addition, chemical breakdown from excessive operating temperatures introduces corrosive acidic compounds that deteriorate synthetic elastomeric seals. Routine sampling and multipath filtration protocols are therefore strictly enforced to maintain fluid purity.

Which of the following statements best expresses the main idea of the passage?

Show answer & explanation

Answer: Contaminated hydraulic fluid is the leading cause of component wear and system malfunction in aircraft flight controls.

Answer

Contaminated hydraulic fluid is the leading cause of component wear and system malfunction in aircraft flight controls.
The passage explicitly begins with the primary claim that hydraulic fluid contamination is the leading source of mechanical degradation and valve failure in flight control systems. The rest of the paragraph describes the physical and chemical damage caused by this contamination, confirming that the statement highlighting contaminated hydraulic fluid as the main cause of component wear and malfunction is the central idea.

Step-by-Step Solution

1
Locate the explicit topic sentence within the paragraph.
The opening sentence directly states that hydraulic fluid contamination is the primary cause of mechanical degradation and valve failure in modern aircraft flight control systems.
In expository passages, the central claim is frequently introduced in the initial lead sentence.
2
Evaluate subsequent sentences to verify whether they support this central claim.
The remaining sentences detail specific mechanisms of contamination damage (particulate abrasion and chemical degradation) and protective maintenance protocols.
Supporting details serve to explain, illustrate, or prove the overarching main idea.
3
Select the option that encapsulates the overall message rather than an isolated fact or broad exaggeration.
The choice identifying contaminated hydraulic fluid as the leading cause of component wear and system malfunction matches the explicit topic sentence.
A valid main idea statement covers the full scope of the passage without being too narrow or too broad.

Key Concept

Identifying Explicit Main Ideas in Expository Paragraphs
Estimated Time:1m 0s
Question 9Question →

Thermal imaging cameras have become an indispensable tool for shipboard firefighting teams. These handheld devices allow firefighters to locate the seat of a fire through dense smoke that completely blocks visible light. In addition, thermal cameras can detect hot spots hidden behind bulkheads before flames spread to adjacent compartments. By displaying infrared radiation as a visible image, the technology also enables rescue teams to quickly find trapped personnel in zero-visibility conditions.

Which of the following statements best expresses the main idea of the passage?

Show answer & explanation

Answer: Thermal imaging cameras are an essential tool for shipboard firefighting operations.

Answer

Thermal imaging cameras are an essential tool for shipboard firefighting operations.
The correct answer directly restates the explicit main idea presented in the opening sentence of the paragraph: thermal imaging cameras are indispensable (essential) for shipboard firefighting teams. Every other sentence in the passage provides supporting evidence explaining how and why these cameras are essential.

Step-by-Step Solution

1
Identify the topic sentence that states the central claim of the passage.
The first sentence explicitly states that thermal imaging cameras are an indispensable tool for shipboard firefighting teams.
Explicit main ideas are directly stated in an identifiable sentence, often at the beginning of the paragraph.
2
Verify that subsequent sentences provide supporting details for this central claim.
The remaining sentences detail specific uses of the cameras: finding the source of a fire, checking behind bulkheads, and locating personnel.
A valid main idea must encompass all supporting examples rather than focusing on just one function.
3
Select the option that accurately paraphrases the explicit topic sentence.
The option stating that thermal imaging cameras are an essential tool for shipboard firefighting operations matches the topic sentence.
Paraphrasing the opening claim confirms comprehension of the overall paragraph.

Key Concept

Identifying an explicitly stated main idea in an introductory topic sentence
Estimated Time:45s
Question 10Question →

Passage:
Synthetic engine oils provide superior thermal stability compared to conventional petroleum-based lubricants in military ground vehicles. While conventional oils break down and form sludge when subjected to sustained high operating temperatures, synthetic formulas maintain their protective viscosity across severe temperature extremes. This chemical resilience minimizes engine wear and extends the operational lifespan of heavy transport vehicles during demanding desert missions.

Statement: According to the passage, the explicitly stated main idea is that synthetic engine oils offer superior thermal stability compared to conventional petroleum lubricants in military ground vehicles.

Show answer & explanation

Answer: True

Answer

True
The statement accurately identifies the explicitly stated main idea because the opening sentence clearly introduces the primary claim regarding the superior thermal stability of synthetic engine oils over petroleum-based lubricants.

Step-by-Step Solution

1
Locate the explicit topic sentence that states the central point of the paragraph.
The first sentence directly states that synthetic engine oils provide superior thermal stability compared to conventional petroleum-based lubricants in military ground vehicles.
In standard expository paragraphs, the explicit main idea is frequently established directly in the opening topic sentence.
2
Compare the provided statement with the identified topic sentence and supporting context.
The statement accurately reflects the overarching claim of the text.
Specific mentions of sludge reduction and desert operations are supporting details that illustrate the primary assertion rather than replace it.

Key Concept

An explicit main idea is directly stated within the text, usually in a topic sentence, and serves as the overarching concept that all supporting facts and details develop.
Question 11Question →

Read each technical excerpt and match it to the statement that expresses its explicitly stated main idea.

Click a left item, then click its matching right item

Items

Active Electronically Scanned Array (AESA) radar systems require specialized closed-loop liquid cooling to prevent severe thermal throttling during high-power target tracking. As hundreds of solid-state transmit-receive modules operate simultaneously, they generate substantial heat flux that conductive air cooling cannot manage. Circulating dielectric fluid through micro-channel cold plates stabilizes internal junction temperatures below eighty degrees Celsius. Without this active thermal dissipation, frequency drift and total module shutdown rapidly occur.
Laminated ceramic-matrix composite panels enhance ballistic protection by breaking apart incoming kinetic penetrators upon impact. The ultra-hard boron carbide strike face shatters the tip of hardened steel or tungsten rounds, dispersing kinetic energy over a wider surface. A backing layer of ultra-high-molecular-weight polyethylene then absorbs the residual fragments and deformation wave without catastrophic structural failure. This dual-action design delivers superior stopping power while significantly reducing overall vehicular weight.
Automated inventory reconciliation is essential for eliminating logistics bottlenecks at forward operating distribution hubs. When tactical supply units manually log munitions, rations, and replacement components, transcription delays inevitably lead to inaccurate depot counts and misallocated transport sorties. Integrating automated optical scanners and localized real-time tracking databases ensures immediate ledger verification across all shipping manifests. Maintaining continuous digital visibility guarantees that frontline combat elements receive critical supplies without operational delays.

Matches

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Answer

The excerpt discussing radar modules matches the statement regarding liquid cooling preventing thermal throttling; the excerpt discussing composite armor matches the statement regarding panels shattering penetrators on impact; and the excerpt discussing supply manifests matches the statement regarding automated inventory reconciliation preventing logistics delays.
Each passage presents an explicit topic sentence in its lead position that states the overall thesis: liquid cooling preventing AESA radar thermal throttling, composite armor shattering kinetic penetrators, and automated inventory reconciliation preventing field logistics delays. The paired statements directly reflect these explicitly stated claims.

Step-by-Step Solution

1
Analyze the first excerpt to identify its primary focus and explicitly stated topic sentence.
The first sentence directly claims that AESA radar systems require closed-loop liquid cooling to prevent thermal throttling, with subsequent sentences providing technical details about dielectric fluid and module temperatures.
Identifying the topic sentence isolates the core claim from supporting operational details.
2
Analyze the second excerpt for its central governing thesis.
The opening sentence explicitly states that laminated ceramic-matrix composite panels enhance ballistic protection by breaking apart penetrators, supported by descriptions of boron carbide and polyethylene layers.
Differentiating the central assertion from component-level descriptions ensures accurate matching.
3
Analyze the third excerpt to determine its explicit central proposition.
The lead sentence states that automated inventory reconciliation is essential for eliminating logistics bottlenecks, while remaining lines elaborate on optical scanners and manual logging risks.
Connecting the topic sentence to its exact thematic match confirms the correct pairing.

Key Concept

Identifying explicitly stated main ideas in expository paragraphs
Question 12Question →

Desiccant packs are essential for protecting sensitive electronic equipment from moisture damage during prolonged storage. When placed inside sealed transit containers, these silica-based packets continuously absorb ambient humidity from the trapped air. By maintaining a dry internal environment, they prevent corrosion on delicate circuit boards and inhibit fungal growth on wiring insulation. Many desiccant packets also include visual indicator beads that change color when saturated, signaling that the material must be reactivated or replaced.

Which of the following statements best expresses the main idea of the passage?

Show answer & explanation

Answer: Desiccant packs play a vital role in safeguarding stored electronics from moisture-related degradation.

Answer

Desiccant packs play a vital role in safeguarding stored electronics from moisture-related degradation.
The passage opens with the explicit topic sentence asserting that desiccant packs are essential for protecting sensitive electronic equipment from moisture damage during storage. Every subsequent sentence describes the specific mechanisms by which these packets control humidity and protect components, making the statement regarding their vital protective role the definitive main idea.

Step-by-Step Solution

1
Locate the explicit topic sentence in the paragraph.
The opening sentence directly states that desiccant packs are essential for protecting sensitive electronic equipment from moisture damage during storage.
Expository paragraphs frequently state their core thesis or main idea in the leading sentence.
2
Evaluate the subsequent sentences to ensure they serve as supporting details.
Sentences discussing humidity absorption, corrosion prevention, fungal inhibition, and color-changing indicator beads all provide specific examples of how the packets achieve moisture protection.
Confirming that all other sentences elaborate on the opening claim verifies that the opening sentence is the overarching main idea.
3
Match the core thesis to the option that accurately paraphrases it without altering scope.
The statement expressing that desiccant packs safeguard stored electronics from moisture-related degradation accurately reflects the primary claim.
The correct answer must represent the entire passage rather than an isolated detail or an unjustified generalization.

Key Concept

An explicit main idea is directly stated in a topic sentence within the text, usually at the beginning, middle, or end of the paragraph, and is supported by all surrounding details.
Estimated Time:45s
Question 13Question →

In heavy-duty turbocharged diesel engines, compressing intake air significantly raises its temperature, which reduces air density and impairs combustion efficiency. Routing this compressed air through an intercooler extracts excess thermal energy before the air reaches the combustion cylinders. By lowering intake air temperature, the intercooler increases air density, delivering a greater mass of oxygen into the cylinders to directly improve combustion efficiency. Although intercoolers add physical weight and require periodic inspection for airflow blockages, their cooling function remains essential for maximizing engine power and fuel economy.

Which of the following statements best expresses the main idea of the passage?

Show answer & explanation

Answer: Intercoolers enhance turbocharged engine performance by cooling intake air to increase its density and combustion efficiency.

Answer

Intercoolers enhance turbocharged engine performance by cooling intake air to increase its density and combustion efficiency.
The correct statement captures the explicit topic sentence of the passage: the essential purpose and function of an intercooler is to cool compressed intake air, thereby increasing its density and oxygen content to boost combustion efficiency and overall performance.

Step-by-Step Solution

1
Read the passage and locate the central thesis or explicit topic sentence.
Identified the explicit statement: 'By lowering intake air temperature, the intercooler increases air density, delivering a greater mass of oxygen into the cylinders to directly improve combustion efficiency.'
An explicit main idea is directly articulated within the text and encapsulates the core function being explained.
2
Distinguish the overarching point from supporting details, secondary qualifications, and extreme scope extrapolations.
Noted that mentions of compression heating, unit weight, and maintenance are supporting context and secondary points serving the main explanation of intercooler function.
Eliminating narrow supporting details and unsupported broad statements isolates the central concept.
3
Select the option that directly matches the explicit main idea without altering scope.
The statement describing how intercoolers enhance performance by cooling air to improve density and combustion efficiency matches the passage precisely.
This captures both the mechanism and the ultimate purpose stated explicitly in the text.

Key Concept

Identifying an Explicit Main Idea in Expository Technical Prose
Estimated Time:1m 0s
Question 14Question →

Foreign Object Debris (FOD) prevention is vital for maintaining aircraft flight safety on military airfields. Stray items such as loose bolts, safety wire, tools, and small stones can be sucked into jet turbine intakes or puncture aircraft tires during takeoff. Ground crews perform daily visual inspections, known as FOD walks, and operate specialized vacuum sweeper trucks across runways and taxiways to remove these hazards. In addition, maintenance personnel must strictly inventory all tools before and after servicing an aircraft to ensure nothing is left behind. Through rigorous inspections and tool control, personnel prevent costly mechanical damage and protect pilot safety.

Which of the following statements best expresses the explicitly stated main idea of the passage?

Show answer & explanation

Answer: Preventing foreign object debris is essential to preserving aircraft safety on military airfields.

Answer

Preventing foreign object debris is essential to preserving aircraft safety on military airfields.
The passage opens with a direct topic sentence establishing that FOD prevention is vital for airfield flight safety, and all subsequent sentences describe specific hazards and measures taken to accomplish that goal.

Step-by-Step Solution

1
Locate the explicit topic sentence
The opening sentence directly states that Foreign Object Debris (FOD) prevention is vital for maintaining aircraft flight safety on military airfields.
Explicit main ideas in technical expository texts are commonly anchored in the opening topic sentence.
2
Evaluate the remaining sentences against the topic sentence
All subsequent sentences provide supporting examples of hazards, sweeping procedures, and tool inventory controls that serve this core goal.
Verifying that every detail develops the central assertion confirms the main idea.

Key Concept

Identifying explicitly stated topic sentences and distinguishing overarching claims from supporting procedural details.
Estimated Time:45s
Question 15Question →

In modern tactical communication networks, the proliferation of asymmetric encryption has significantly enhanced data security across distributed nodes. However, the sheer volume of generated cryptographic keys introduces substantial logistical overhead during rapid deployment scenarios. To maintain operational tempo, automated key management systems must dynamically allocate decryption protocols without requiring manual intervention from field operators. Consequently, the primary challenge in tactical cryptography is no longer encryption strength, but rather the seamless distribution and lifecycle management of cryptographic keys across volatile network environments. Advanced algorithms now prioritize this distribution efficiency, recognizing that even the most robust cipher is tactically useless if the intended recipient cannot securely and swiftly access the corresponding key.

Which of the following statements best expresses the main idea of the passage?

Show answer & explanation

Answer: The central difficulty in tactical cryptography has shifted from encryption strength to the efficient distribution and management of keys.

Answer

The central difficulty in tactical cryptography has shifted from encryption strength to the efficient distribution and management of keys.
The correct answer accurately reflects the sentence explicitly anchoring the passage: 'Consequently, the primary challenge in tactical cryptography is no longer encryption strength, but rather the seamless distribution and lifecycle management of cryptographic keys...' It synthesizes the paragraph's focus on the logistical hurdles of cryptography rather than the encryption itself.

Step-by-Step Solution

1
Analyze the paragraph structure and flow of information.
The passage begins with background context, introduces a complication, proposes a requirement, and then synthesizes these points into a conclusive statement.
Understanding paragraph structure helps distinguish between supporting details, context, and the central thesis.
2
Identify transition words that signal the author's primary point.
The word 'Consequently' signals the author's main conclusion: 'the primary challenge... is no longer encryption strength, but rather the seamless distribution...'
Authors often use transitional adverbs to explicitly state their main idea after providing the necessary background.
3
Evaluate the answer choices against the identified explicit main idea.
The correct option correctly paraphrases the 'Consequently' sentence, capturing the shift in focus from encryption strength to key management.
The correct answer in an explicit main idea question must directly reflect the core topic sentence without being too broad or focusing on a minor detail.

Key Concept

Identifying the Explicit Main Idea in Dense Technical Prose
Estimated Time:1m 30s
Question 16Question →

Passage:
On-Board Inert Gas Generation Systems (OBIGGS) protect military aircraft fuel tanks from catastrophic ignition by continuously displacing volatile oxygen with nitrogen-enriched air. During operational flights, fuel consumption creates an expanding ullage space inside fuel tanks that accumulates flammable hydrocarbon vapors. Without active inerting, electrostatic discharges or ballistic impacts could easily ignite this fuel-air mixture. By utilizing semipermeable hollow-fiber membranes to separate oxygen from compressed engine bleed air, OBIGGS delivers nitrogen-enriched gas directly into the tank ullage, maintaining oxygen concentrations safely below combustion thresholds.

Statement: The explicitly stated main idea of the passage is that OBIGGS safeguards aircraft fuel tanks against explosion by replacing oxygen with nitrogen-enriched air.

Show answer & explanation

Answer: True

Answer

True
The statement is correct because the lead sentence explicitly asserts that OBIGGS protects aircraft fuel tanks from ignition by displacing oxygen with nitrogen-enriched air, and all subsequent sentences provide supporting context for this central claim.

Step-by-Step Solution

1
Locate the explicit topic sentence that defines the primary subject and assertion of the passage.
The first sentence directly states that On-Board Inert Gas Generation Systems (OBIGGS) protect military aircraft fuel tanks from catastrophic ignition by continuously displacing volatile oxygen with nitrogen-enriched air.
In expository and technical paragraphs, the explicit main idea is directly articulated by the author, frequently in the opening sentence.
2
Compare the provided statement against the identified explicit main idea.
The statement precisely matches the central claim regarding the purpose and mechanism of OBIGGS.
The supporting sentences elaborate on the hazard (flammable ullage space) and the technical process (membranes separating bleed air), both reinforcing the primary claim.

Key Concept

Explicit Main Idea Identification
Estimated Time:1m 0s
Question 17Question →

Read the three technical maintenance excerpts below. Match each technical excerpt to the statement that directly expresses its explicit main idea.

Click a left item, then click its matching right item

Items

Lead-acid storage batteries require regular specific gravity testing of their electrolyte to accurately determine their state of charge. Technicians use a hydrometer to sample the sulfuric acid solution from each individual battery cell. As a battery discharges, sulfate ions leave the liquid and bind to lead plates, decreasing electrolyte density. Measuring this fluid density provides a direct and reliable assessment of remaining electrical energy.
Routine torque wrench calibration is essential for ensuring that mechanical fasteners deliver the precise clamping force required for structural integrity. Over repeated mechanical cycles, internal spring tension and ratcheting mechanisms experience measurement drift. If tools are not routinely tested against certified transducers and adjusted to standard tolerances, under-torqued bolts may loosen under operational vibration or over-torqued fasteners may suffer premature shear failure.
Electrically heated pitot-static probes prevent ice accumulation that compromises critical airspeed and altitude flight instrumentation. During flight through freezing moisture or sub-zero clouds, ice buildup can rapidly obstruct the forward dynamic pressure port and lateral static ports. Internal resistive heating elements continuously maintain exterior surface temperatures above freezing, ensuring clear airflow and reliable instrument data.

Matches

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Answer

The excerpt discussing battery electrolyte matches the statement regarding specific gravity testing for state of charge; the excerpt on torque wrench calibration matches the statement regarding maintaining proper fastener clamping force; and the excerpt on heated pitot-static probes matches the statement regarding preventing ice formation on flight instrumentation.
Each excerpt contains a clearly identifiable explicit topic sentence at its beginning that summarizes the central purpose and scope of the text. The statement regarding electrolyte specific gravity directly matches the core focus of the battery passage; the statement regarding calibration for clamping force directly matches the torque wrench passage; and the statement regarding ice prevention on flight instruments directly matches the pitot-static probe passage.

Step-by-Step Solution

1
Analyze the lead sentence and scope of the first excerpt regarding lead-acid storage batteries.
Identified the explicit topic sentence: 'Lead-acid storage batteries require regular specific gravity testing of their electrolyte to accurately determine their state of charge.'
Explicit main ideas in technical expository paragraphs are directly stated, commonly in the introductory sentence.
2
Analyze the lead sentence and supporting details of the second excerpt regarding torque wrenches.
Identified the explicit topic sentence: 'Routine torque wrench calibration is essential for ensuring that mechanical fasteners deliver the precise clamping force required for structural integrity.'
The supporting sentences detail the mechanisms of measurement drift and fastener failure, illustrating the central claim stated in the opening sentence.
3
Analyze the lead sentence and technical context of the third excerpt regarding pitot-static probes.
Identified the explicit topic sentence: 'Electrically heated pitot-static probes prevent ice accumulation that compromises critical airspeed and altitude flight instrumentation.'
The subsequent text elaborates on the mechanism of resistive heating elements and port obstruction, directly supporting the primary explicit claim.
4
Match each analyzed excerpt with its corresponding explicit main idea summary statement.
Confirmed all three correct 1-to-1 pairings.
Each statement directly restates the exact primary assertion of its corresponding excerpt without introducing unsupported inferences or narrow supporting details.

Key Concept

Identifying an explicitly stated topic sentence that captures the primary claim and complete scope of an expository paragraph.
Estimated Time:1m 30s
Question 18Question →

In modern military and commercial aviation, fuel tank ullage—the empty volume above liquid fuel—contains flammable hydrocarbon vapors that pose severe explosion hazards if exposed to electrical arcing or static discharge. While mechanical flame arrestors and reinforced bladders mitigate certain localized risks, onboard inert gas generation systems (OBIGGS) remain the primary defense against fuel tank ignition by continuously displacing oxygen with nitrogen-enriched air. These systems utilize permeable hollow-fiber membranes to separate and vent oxygen molecules from pressurized bleed air, driving ullage oxygen concentrations below nine percent by volume. Consequently, establishing an inert atmosphere through active nitrogen displacement prevents catastrophic vapor detonation under varying flight altitudes and operational temperatures.

Which of the following statements most accurately expresses the main idea explicitly stated in the passage?

Show answer & explanation

Answer: Onboard inert gas generation systems serve as the principal protection against fuel tank ignition by displacing oxygen with nitrogen.

Answer

Onboard inert gas generation systems serve as the principal protection against fuel tank ignition by displacing oxygen with nitrogen.
The passage explicitly states that while other methods address localized hazards, onboard inert gas generation systems (OBIGGS) remain the primary defense against fuel tank ignition by displacing oxygen with nitrogen-enriched air. The correct option directly paraphrases this central claim.

Step-by-Step Solution

1
Analyze the structural organization of the passage to locate the central topic assertion.
Identified the explicit thesis stated in the second sentence: onboard inert gas generation systems (OBIGGS) are the primary defense against fuel tank ignition by displacing oxygen with nitrogen-enriched air.
An explicit main idea is directly articulated within an identifiable topic sentence rather than implied.
2
Differentiate the overarching claim from subordinate technical details and secondary countermeasure mentions.
Membrane mechanics, oxygen percentage thresholds, and mechanical arrestors serve solely as supporting evidence illustrating how and why nitrogen displacement functions as the primary protective measure.
Supporting details elaborate on the mechanism but do not encapsulate the complete central purpose of the text.
3
Evaluate the options to find the exact conceptual match that avoids scope distortions and detail traps.
The statement identifying OBIGGS as the principal defense against fuel tank ignition via nitrogen displacement precisely matches the topic sentence.
The correct option must encompass the main idea without narrowing to a single detail or generalizing beyond the text.

Key Concept

Explicit Main Idea Identification
Estimated Time:1m 15s
Question 19Question →

Read each technical excerpt regarding military equipment maintenance and field operations. Match each passage to the statement that expresses its explicitly stated main idea.

Click a left item, then click its matching right item

Items

Type I aircraft de-icing fluids are formulated primarily to remove existing ice and snow from aerodynamic surfaces before takeoff. These fluids are applied hot and under high pressure to melt frozen deposits quickly. Because they possess low viscosity, they shear off the aircraft rapidly during takeoff roll, providing minimal ongoing protection against fresh accumulation.
White phosphor displays provide operators with superior visual contrast and reduced eye fatigue compared to traditional green phosphor night vision devices. Although green phosphor was historically standard due to peak human eye sensitivity, modern white phosphor technology significantly enhances target discrimination in low-contrast tactical environments during extended night missions.
Portable ceramic water filters physically eliminate bacterial pathogens and suspended sediment from untreated field water without requiring chemical additives. As raw water is pumped through the microporous ceramic membrane, microscopic physical barriers block contaminants larger than 0.2 microns, ensuring immediate potable water in austere operational environments.

Matches

Show answer & explanation

Answer

Match the de-icing fluid excerpt to the statement regarding melting and clearing existing ice before takeoff; match the night vision excerpt to the statement regarding improved contrast and reduced eye fatigue; match the water filtration excerpt to the statement regarding physical removal of bacteria and sediment without chemicals.
Each passage features an explicit lead topic sentence that articulates the core function or advantage of the subject. Matching these opening statements to their direct restatements correctly identifies each passage's explicitly stated main idea.

Step-by-Step Solution

1
Read the opening sentence of each passage to locate the explicitly stated topic sentence.
Identified that each technical passage presents its core main idea directly in its first sentence.
An explicit main idea is directly articulated in the text rather than left implied.
2
Pair each topic sentence with its corresponding summary statement while distinguishing main ideas from supporting technical details.
Correctly matched all three passages to their corresponding main idea statements.
Details such as fluid shearing rates, wavelength sensitivities, and micron pore sizes provide supporting mechanisms rather than the central claim.

Key Concept

Explicit Main Idea Identification
Estimated Time:55s
Question 20Question →

Passage:
During scheduled depot-level maintenance, aviation technicians frequently inspect critical airframe joints for microscopic fatigue damage using specialized electromagnetic probes. By passing an energized coil over aluminum skin panels, the instrument induces circular electrical currents that experience measurable resistance changes whenever a subsurface flaw is encountered. Because it reliably identifies minute defects without damaging components or requiring disassembly, eddy-current testing has become an essential non-destructive inspection method for military aircraft.

According to the passage, which of the following best expresses the main idea?

Show answer & explanation

Answer: Eddy-current testing is an indispensable non-destructive method for detecting structural defects in military aircraft.

Answer

Eddy-current testing is an indispensable non-destructive method for detecting structural defects in military aircraft.
The correct answer accurately restates the explicit topic sentence found at the end of the passage, which establishes that eddy-current testing is a vital non-destructive evaluation tool for military aircraft structural integrity.

Step-by-Step Solution

1
Read the passage to identify the central topic and overall scope.
The text discusses how maintenance technicians inspect airframes using electromagnetic probes to detect hidden structural fatigue.
Grasping the paragraph as a whole prevents mistaking individual technical details for the primary message.
2
Locate the explicit topic sentence that synthesizes the supporting facts.
The concluding sentence states that eddy-current testing has become an essential non-destructive inspection method for military aircraft because it detects defects without component disassembly or damage.
In technical expository prose, the main idea is often explicitly stated in a concluding topic sentence that summarizes the function and importance of the subject.
3
Match the explicit claim to the corresponding option while eliminating narrow details and scope distortions.
The statement identifying eddy-current testing as an indispensable non-destructive method for detecting structural defects accurately captures the explicit topic sentence.
The correct choice must capture the entire paragraph's primary thesis rather than an isolated operational step or an overgeneralized claim.

Key Concept

Explicit Main Idea Identification
Estimated Time:1m 0s
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Explicit Main Idea Practice Questions — Armed Services Vocational Aptitude Battery (ASVAB) | Examkin