All practice questions

The archerfish is a remarkable freshwater fish found in the mangrove swamps of South and Southeast Asia. What makes the archerfish unique is its ability to hunt land-based insects by shooting them down with a precise stream of water. To achieve this, the archerfish presses its tongue against a groove in the roof of its mouth, forming a tube that acts like a gun barrel. It then squeezes its gills to force water out of the tube, creating a powerful jet. The fish can accurately hit prey up to two meters away. Additionally, the archerfish is capable of compensating for light refraction at the water's surface, adjusting its aim instantly to hit its target. While it also feeds on typical aquatic prey like smaller fish and insects floating on the water, its specialized spitting technique is its primary and most distinctive method of securing food. Scientists study this behavior to understand how complex visual-motor coordination can evolve in relatively simple organisms.

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

For decades, silviculturists studying temperate and tropical forests have been fascinated by 'crown shyness'—a phenomenon where the uppermost branches of neighboring trees avoid touching, creating a network of canopy gaps that resemble narrow pathways. While several theories have been proposed to explain this behavior, recent research has clarified the precise physiological mechanisms behind it. When wind causes adjacent tree branches to collide, the physical impact breaks the delicate growing tips of the branches, particularly the tender nodules of young leaves. In response to this mechanical abrasion, the trees halt lateral growth in those specific directions, resulting in the permanent gaps that define crown shyness. Interestingly, some researchers hypothesized that this spacing might also serve as a defense mechanism to prevent the spread of leaf-eating insects. However, controlled field studies have demonstrated that the primary catalyst remains the physical friction caused by wind-induced motion, rather than a proactive evolutionary adaptation to pests. Consequently, in regions sheltered from heavy wind, even dense stands of these species show significantly less crown shyness, with branches overlapping freely.

Based on the passage, what is the direct cause of the permanent gaps that characterize crown shyness in tree canopies?

While earlier civilizations built channels to transport water, the Romans revolutionized hydraulic engineering through the utilization of pozzolana, a volcanic ash found near Mount Vesuvius. When combined with lime, this material created a highly durable underwater concrete that allowed Roman engineers to construct massive, multi-tiered aqueduct bridges across wide valleys and turbulent rivers. Unlike modern concrete, which degrades relatively quickly when exposed to moisture, pozzolana concrete actually grew stronger over time due to a chemical reaction between the seawater and the volcanic minerals. This unique crystalline structure prevented the propagation of microscopic cracks, ensuring that the aqueducts remained functional for centuries with minimal structural maintenance, thereby securing a consistent water supply for the empire’s rapidly growing urban centers.

According to the passage, how did Roman pozzolana concrete differ from the concrete used in modern times?

The Andean Altiplano, a high-altitude plateau spanning parts of modern Bolivia and Peru, presents a notoriously harsh environment characterized by intense solar radiation, thin air, and extreme diurnal temperature fluctuations. To thrive in this arid landscape, the ancient Tiwanaku culture developed sophisticated agricultural and preservation techniques, most notably the production of chuño—a freeze-dried potato product that could be stored for years. The creation of chuño relied entirely on the region's unique microclimate. During the Andean winter nights, temperatures regularly plummeted below freezing, which crystallized the water content inside the harvested tubers. The subsequent daytime sun exposure, combined with the low atmospheric pressure of the Altiplano, allowed this frozen moisture to sublimate directly into vapor without returning to a liquid state. By bypassing the liquid phase, the potatoes were effectively dehydrated before rot-inducing bacteria could proliferate. Additionally, the physical trampling of the potatoes by Tiwanaku farmers during the transition between freezing and thawing cycles was crucial: this mechanical pressure ruptured the potato cell walls, forcing out remaining cellular liquids and preventing the formation of large ice crystals that would otherwise degrade the starch structures. Consequently, the resulting chuño retained its nutritional value and structural integrity, serving as a reliable safeguard against crop failures and seasonal famines.

Based on the passage, the degradation of the potatoes' starch structures during the production of chuño was prevented as a direct result of which of the following?

In the winter of 1845, Maria Mitchell spent every clear evening on the roof of the Pacific Bank in Nantucket. While other young women of her class occupied themselves with needlework or society gossip, Mitchell kept her eyes trained on the northern skies, meticulously recording the positions of stars. Her father, a cashier at the bank, had recently moved the family into the residential quarters located directly beneath the rooftop terrace. He spent his evenings teaching Maria to use the sextant, away from the quiet whispers of the town below. On the night of October 1, 1847, Maria noticed a faint, blurry object that did not appear on any of her charts. She had discovered a comet, earning a gold medal from King Christian VIII of Denmark. Although she was celebrated abroad, at home her work remained confined to the bank's roof—a space her father had secured through his employment, shielding her studies from a society that viewed a young woman wandering the night streets as highly improper.

In the context of the passage, which of the following best describes the father's primary motivation for moving the family into the residential quarters at the bank?

The following passage is adapted from an essay exploring the philosophy of cognitive science.

Paragraph 1 (lines 1-12)
Philosophers of mind have traditionally treated the boundary of the skull as the absolute limit of the human cognitive system. Under this internalist paradigm, mental processes—such as remembering, calculating, and planning—are strictly neural events occurring entirely within the brain. External tools, from simple notebooks to sophisticated digital calculators, are viewed merely as passive inputs or outputs that assist an already complete cognitive agent, rather than constituting active parts of the cognitive process itself.

Paragraph 2 (lines 13-25)
However, in their seminal 1998 paper, philosophers Andy Clark and David Chalmers proposed the "Extended Mind" thesis, arguing that the mind does not stop at the skin and skull. They suggest that when external objects are functionally integrated into our decision-making loops, they become literal components of our cognitive machinery. If a patient with Alzheimer's disease relies on a notebook to store memories and navigate daily life, that notebook performs the same functional role as biological memory. Therefore, Clark and Chalmers assert that the notebook is not just a tool; it is a physical constituent of the patient's mind.

Paragraph 3 (lines 26-42)
While critics often dismiss this thesis as a mere semantic redefinition of "mind," supporters argue it represents a fundamental shift in how we analyze human agency. By extending the cognitive boundary outward, we are forced to reconsider the relationship between technology and selfhood. Under this view, a smartphone is not merely an external device we manipulate; it is an active partner in a single, distributed cognitive system. Consequently, the ethical implications of this shift are profound: tampering with a person's digital device might be construed not simply as property damage, but as a direct assault on their cognitive integrity.

Which of the following best states the main idea of Paragraph 3 (lines 26-42)?

The following passage is adapted from an article about the history of molecular biology:

For decades, the central dogma of molecular biology dictated that infectious agents must contain nucleic acids—either DNA or RNA—to replicate and cause disease. When Stanley Prusiner first proposed in 1982 that the transmissible agent behind scrapie, a degenerative neurological disease, was composed entirely of protein, the scientific community met his hypothesis with profound skepticism. To support his radical claim, Prusiner demonstrated that procedures damaging to nucleic acids, such as ultraviolet radiation, failed to reduce the infectivity of the scrapie agent, whereas treatments that denatured proteins, such as exposure to urea, rendered the agent inactive. Critics argued that the protein-only model violated fundamental biological principles, suggesting instead that a small, hidden virus was the true culprit. However, the subsequent discovery of the gene encoding the prion protein (PrP) in healthy organisms eventually clarified the mechanism: the disease arises when the normal cellular protein misfolds into a pathological, self-propagating shape. By redefining the biochemical basis of infection, the prion hypothesis fundamentally transformed our understanding of neurodegenerative diseases, demonstrating that structural replication could occur in the absence of genetic material.

Which statement best summarizes the author's primary argument in the passage?

Passage A
In the late nineteenth century, the Pictorialist movement sought to elevate photography to the status of fine art by emphasizing the photographer's personal vision over the camera's ability to record reality. Pictorialists like Alfred Stieglitz (in his early career) and Gertrude Käsebier achieved this by employing soft-focus lenses, textured papers, and chemical manipulations during the printing process. Their goal was to produce images that resembled charcoal drawings or impressionistic paintings. For Pictorialists, the mechanical precision of the camera was an obstacle to true artistic expression; they believed that art resided in the subjective modification of the raw image, transforming a mechanical document into a vehicle for emotional and poetic truth.

Passage B
By the early twentieth century, a new vanguard rejected the painterly aspirations of Pictorialism in favor of "Straight Photography." Proponents of this movement, including Paul Strand and the later Stieglitz, argued that photography should be celebrated for its unique, inherent qualities rather than forced to mimic older visual media. They advocated for sharp focus, high contrast, and unmanipulated prints that captured the precise geometries and textures of the modern world. In their view, true photographic art came from recognizing the expressive potential of the machine itself. Rather than trying to obscure the camera's mechanical nature, straight photographers embraced it, using precision to reveal truths invisible to the naked or subjective eye.

Based on the passages, which of the following best describes how Passage A and Passage B differ in their characterization of the camera's mechanical precision?

To analyze trace chemical constituents in polar ice cores without contamination, glaciologists must execute a rigorous decontamination protocol in a clean room. First, the core sections, which are retrieved from the field wrapped in polyethylene, are mechanically scraped inside a clean-air hood. Technicians use a pre-cleaned band saw to shave off the outer $15\%$ of the core's radius, which has been exposed to drilling fluids. Following this dry scraping, the core segment is subjected to a sequential washing sequence using ultra-pure water. The segment is rinsed three times in separate baths of deionized water ($> 18.2\text{ M}\Omega\cdot\text{cm}$) maintained at $1^\circ\text{C}$ to melt away another thin outer layer. Crucially, the segment must be immediately dried under a stream of high-purity nitrogen gas after the final rinse. If the drying step is omitted or delayed, the residual wash water will refreeze on the core surface, capturing ambient gases and dust from the clean room air and compromising the subsequent mass spectrometry analysis. Only after complete drying is the remaining inner core melted in a Teflon beaker under vacuum for isotopic analysis.

Based on the passage, what is the direct consequence of omitting the high-purity nitrogen gas drying step during the ice core decontamination protocol?

To isolate microplastics from marine sediment samples for environmental analysis, researchers must follow a strict, multi-step density separation and filtration protocol. First, the sediment sample is dried in an oven at $60^\circ\text{C}$ to remove all moisture without melting the synthetic polymers. Once dried, the sample is mixed with a high-density salt solution, typically sodium iodide ($\text{NaI}$), which has a density of $1.8\text{ g/cm}^3$. This density is crucial because it allows the lighter plastic particles to float while the heavier mineral sands sink to the bottom. After thorough stirring, the mixture is left to settle for at least $24\text{ hours}$. Subsequently, the supernatant—the top liquid layer containing the floating microplastics—is carefully decanted into a vacuum filtration apparatus fitted with a $0.45\text{-micrometer}$ glass fiber filter. It is essential to perform this decanting step prior to adding any organic digestants; introducing hydrogen peroxide to the mixture before separation would cause violent foaming due to the high mineral and organic content of the raw sediment, potentially ejecting the microplastics from the beaker. Finally, the filter containing the collected microplastics is treated with a $30\%$ hydrogen peroxide solution to digest any remaining natural organic matter, leaving the clean microplastics ready for microscopic characterization.

According to the passage, which of the following is the primary risk of introducing hydrogen peroxide to the mixture before performing the decanting step?

To determine the age of archaeological sediments using Optically Stimulated Luminescence (OSL), researchers extract coarse-grain quartz under strictly controlled conditions to prevent resetting the geological signal. Under dim red light, the raw sediment is first sieved to isolate grains between $90$ and $250$ micrometers. Subsequently, the isolated fraction is treated with hydrochloric acid ($\\text{HCl}$) to dissolve carbonates, which could otherwise interfere with subsequent chemical treatments. Once the effervescence ceases, the sample is washed prior to being treated with hydrogen peroxide ($\\text{H}_2\\text{O}_2$) to remove organic matter. Crucially, the remaining minerals are then subjected to a dense liquid separation using sodium polytungstate at a specific gravity of $2.62\\text{ g/cm}^3$ to float off potassium feldspars, which exhibit unwanted luminescence signals. Finally, the remaining heavy fraction is etched with concentrated hydrofluoric acid ($\\text{HF}$) for $40$ minutes. This $\\text{HF}$ etching serves a dual purpose: it dissolves any remaining feldspars and simultaneously etches away the alpha-irradiated outer shell of the quartz grains, leaving pure quartz cores ready for measurement.

Based on the passage, if a researcher omits the dense liquid separation step using sodium polytungstate, which of the following is the most likely consequence for the final quartz sample?

The following passage is adapted from an essay about the social dynamics of eighteenth-century French salons.

Paragraph 1 (lines 1-15)
Historians have long celebrated the French salons of the eighteenth century as the crucibles of the Enlightenment, spaces where intellectual debate supposedly transcended social hierarchies. In these assemblies, hosted primarily by wealthy, aristocratic women, philosophers like Voltaire and Diderot gathered to debate radical ideas about liberty, reason, and governance. Because salon guests were ostensibly judged on their wit and intellect rather than their noble lineage, many scholars argue that the salon served as a precursor to the modern public sphere. In this view, the salon was a democratic haven that dismantled feudal social barriers, facilitating the free exchange of subversive ideas that would ultimately feed the flames of the French Revolution.

Paragraph 2 (lines 16-32)
However, a closer examination of salon correspondence suggests that this idealized portrayal overlooks the rigid social etiquette that governed these gatherings. Far from being democratic forums, salons were highly structured arenas where elite hosts policed the boundaries of polite conversation. To gain entry, participants had to master the intricate codes of bienséance���a complex system of decorum, tone, and conversational restraint. While intellectuals of modest origins were invited, they were expected to conform to aristocratic linguistic norms, effectively silencing those who could not perform this stylized civility. Consequently, rather than democratizing knowledge, the salon functioned primarily to domesticate radical philosophy, rendering it palatable to the very ruling classes whose authority it ostensibly challenged.

Which of the following statements best describes the main idea of the second paragraph (lines 16-32)?

Read the passage below, and then match each individual's action or situation to the implied role or motivation that can be inferred from the text.

Passage Excerpt:
Although the standard account of the 1911 excavation at Machu Picchu credits Hiram Bingham with the sole discovery of the lost city, local records tell a more collaborative story. Months before Bingham arrived, local farmers like Melchor Arteaga had already cleared pathways through the dense vegetation to cultivate crops on the ancient stone terraces. In fact, Arteaga served as Bingham’s guide, leading him directly to the ruins. Meanwhile, Albert Giesecke, the rector of the university in Cusco, had provided Bingham with crucial maps and contacts after hearing rumors of ruins from local travelers. While Bingham’s subsequent publication in National Geographic brought global fame to the site and secured his place in history, the physical labor of clearing the site and the foundational geographical knowledge were quietly contributed by individuals whose names remained in the margins of his travel journals. Bingham’s letters home during this period reveal a man intensely focused on securing institutional funding and academic prestige, often glossing over the contributions of his local companions. Thus, the discovery was not a sudden stroke of individual genius, but the culmination of localized knowledge and guide work that Bingham synthesized and popularized for an international audience.

The following passage is adapted from an article about the biological mechanisms of the human brain.

The Glymphatic System: The Brain's Waste Clearance

Paragraph 1 (lines 1-14)
For decades, neuroscientists were puzzled by how the brain disposes of its metabolic waste. While the rest of the body relies on the lymphatic system to clear cellular debris and excess proteins, the brain lacks traditional lymphatic vessels. This anatomical mystery led researchers to assume that waste clearance in the central nervous system was a slow, passive process of diffusion through cerebrospinal fluid (CSF). However, the discovery of the glymphatic system—a specialized waste clearance network—overturned this long-held assumption, revealing a highly organized, active system driven by fluid flow that flushes toxic waste from the brain.

Paragraph 2 (lines 15-28)
The mechanics of this system depend heavily on glial cells called astrocytes, which wrap their specialized endfeet around the brain's vasculature. These endfeet are rich in water channels that facilitate the rapid movement of CSF from the perivascular spaces directly into the brain tissue. As CSF sweeps through the extracellular space, it collects metabolic waste products, such as amyloid-beta proteins. The waste-laden fluid is then directed toward the perivenous spaces, where it is ultimately exported out of the skull and into the systemic circulation for filtration and disposal by the body's peripheral organs.

Paragraph 3 (lines 29-42)
Intriguingly, the glymphatic system does not operate continuously at peak efficiency; rather, it is highly regulated by the brain's sleep-wake cycle. Research indicates that during sleep, particularly deep slow-wave sleep, the brain’s extracellular space expands by up to sixty percent. This expansion dramatically reduces resistance to fluid flow, allowing CSF to rush through the tissue and clear waste much more rapidly than during waking hours. This sleep-dependent activation explains why chronic sleep deprivation is strongly correlated with the accumulation of neurotoxic proteins and the progression of neurodegenerative disorders.

Based on the passage, match each paragraph to its corresponding paragraph-level main idea.

Before Elisha Otis's invention of the safety elevator in 1852, buildings rarely exceeded five stories. While hoists had existed for centuries to transport goods, they relied on simple hemp ropes that frequently snapped under heavy loads, making passenger travel perilously unsafe. Otis designed a revolutionary safety brake: if the hoisting rope broke, a heavy spring would release, forcing metal teeth on the elevator car to lock into guide rails along the shaft. This automatic mechanism stopped the cabin's fall immediately. By demonstrating this system publicly at the 1854 New York World's Fair, Otis eliminated the widespread fear of falling elevator cabins. Consequently, his safety elevator cleared the path for the construction of modern skyscrapers, permanently transforming the urban landscape.

According to the passage, Otis's safety brake functioned by:

The passage below is adapted from an essay about the history of journalism and communication technology.

[Paragraph 1] (lines 1–14)
Before the electric telegraph, news traveled at the speed of physical transportation. Newspapers were local, partisan, and highly narrative, often filling columns with long-winded essays, gossip, and delayed reports carried by horses or ships. The invention of the telegraph in the 1840s, however, introduced a fee-per-word model that incentivized brevity. Journalists had to transmit the most critical facts first, fearing that wire connections might fail mid-transmission. This technological constraint birthed the "inverted pyramid" style of writing, where the most crucial information is placed at the very beginning of an article.

[Paragraph 2] (lines 15–28)
Furthermore, the telegraph catalyzed the rise of cooperative news gathering, most notably the Associated Press (AP). Because telegraph lines were expensive to lease, independent newspapers could not afford to maintain exclusive national bureaus. By pooling resources to share a single wire service report, competing editors established a shared, objective style of reporting designed to appeal to newspapers of all political affiliations. Consequently, the telegraph did not simply accelerate the transmission of information; it fundamentally reshaped the tone of journalism, shifting it from highly opinionated commentary toward standardized, non-partisan reporting.

[Paragraph 3] (lines 29–41)
Yet, this rapid centralization of information was not without its critics. Some contemporary editors worried that the telegraph-driven press prioritized speed over depth, substituting dry facts for thoughtful analysis. They argued that the new wire reports stripped events of their local color and historical context, reducing complex human dramas to terse, superficial dispatches. By transforming news into a highly commodified, instantaneous product, the telegraph began to separate the act of reporting events from the intellectual work of interpreting their broader cultural meaning.

Based on the passage provided, match each designated paragraph to the statement that best expresses its primary main idea.

The completion of the Aswan High Dam in 1965 dramatically altered the ecology of the Nile River basin and the adjacent eastern Mediterranean Sea. Before the dam's construction, the annual Nile flood carried millions of tons of nutrient-rich silt into the sea. This nutrient influx stimulated a massive seasonal bloom of phytoplankton, which in turn supported a highly productive sardine fishery along the Egyptian coast. Following the dam's closure, however, the annual flood was halted, and the vital nutrients were trapped in Lake Nasser behind the dam. Consequently, the phytoplankton population collapsed due to the sudden starvation of nutrients. Without this primary food source, the Egyptian sardine catch plummeted by more than ninety percent within a single year. While the dam succeeded in providing electricity and flood control, this sudden decline in marine nutrients devastated the local coastal fishing communities that had relied on the seasonal cycles of the river for generations.

According to the passage, what was the direct cause of the collapse of the phytoplankton population in the eastern Mediterranean Sea?

Read the passage below and answer the question that follows.

In the late eighteenth century, French engineer Claude Chappe developed the semaphore telegraph, a visual communication system that revolutionized long-distance messaging. The network consisted of towers positioned within line of sight of one another, each topped with a mechanical apparatus featuring pivoting wooden arms. Operators manipulated these arms into various angles to represent specific letters, numbers, or control signals. Because weather conditions and topography could easily obstruct the view between stations, Chappe designed a codebook containing thousands of pre-defined phrases. This system allowed operators to transmit complex messages using only a few symbols, significantly reducing transmission time. Before the telegraph's deployment, sending a message from Paris to Lille took nearly a day by courier; Chappe’s optical system accomplished the task in under ten minutes, establishing the first nationwide data network.

According to the passage, which of the following is the reason Chappe created a codebook of pre-defined phrases for the semaphore telegraph?

Passage A

For decades, historians of science credited the rapid expansion of early modern metallurgy to the sudden, isolated breakthroughs of individual inventors, who guarded their formulas like guild secrets. In this view, progress was a series of disjointed leaps, punctuated by periods of stagnation. However, recent archival discoveries of correspondence between sixteenth-century alchemists and miners reveal a dense, cross-border network of knowledge exchange. These practitioners did not work in vacuums; rather, they participated in an informal, transnational cooperative where raw data regarding smelting temperatures and ore purity was shared under a tacit agreement of reciprocity. Thus, the growth of the field was cumulative and social, rather than sporadic and individualistic.

Passage B

While the collaborative network of early modern metallurgical practitioners is now well-documented, the nature of their cooperation was far from open or altruistic. To characterize their exchange as a precursor to modern scientific sharing is to misunderstand the intense commercial rivalries of the era. The sharing of metallurgical recipes was a highly strategic, transactional endeavor: information was exchanged only when it was mutually beneficial to secure a patent or outmaneuver a domestic monopoly. Practitioners frequently salted their letters with deliberately misleading instructions to protect their own ventures while extracting secrets from competitors. Cooperation, therefore, did not replace secrecy; rather, secrecy and strategic disclosure operated as complementary tactics in a highly competitive economic landscape.

Based on the passages, which of the following statements best describes the relationship between the two passages' characterizations of early modern metallurgical knowledge exchange?

Read the following passage and answer the question below.

Leafcutter ants are famous for their conspicuous columns, carrying freshly cut green leaves back to their underground nests. However, contrary to popular belief, these ants do not actually eat the leaves. Instead, they use the foliage as a substrate to cultivate a specific species of fungus, Leucoagaricus gongylophorus, which serves as the primary food source for their larvae. This sophisticated agricultural system represents a highly evolved mutualism that has persisted for millions of years. Within the nest, larger worker ants chop the leaves into smaller pieces and chew them into a paste, while smaller workers tend the fungal gardens, weeding out unwanted spores. Additionally, the ants carry a specialized strain of bacteria on their cuticles that produces antibiotics, actively protecting their fungal crops from parasitic molds. Through this coordinated division of labor and chemical defense, leafcutter ant colonies sustain a complex agricultural enterprise that rivals human farming in its efficiency.

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