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Difficulty: HardExplicit Main Idea

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?

  1. A
    Naval engineering protocols mandate speed limits and acoustic monitoring to ensure compliance with operational standards.
  2. B
    Operators identify cavitation primarily by listening for its distinctive acoustic signature and feeling hull vibration.
  3. Cavitation poses a major operational hazard primarily because it causes progressive physical erosion and structural damage to propeller blades.Answer
  4. D
    Marine propulsion systems inevitably suffer catastrophic blade failure whenever localized pressure drops occur in fluid environments.

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
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Explicit Main Idea

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