All practice questions

While both Venus and Mars are neighboring planets of Earth, their atmospheres present stark contrasts. Venus is enveloped in an incredibly dense atmosphere dominated by carbon dioxide, which exerts a crushing pressure on its surface—roughly ninety times that of Earth. This thick layer traps solar energy, raising surface temperatures to scorching levels. Conversely, Mars has a very thin atmosphere, with a surface pressure less than one percent of Earth's. Because this sparse atmosphere cannot retain heat, Mars remains a frozen desert. Thus, while a probe landing on Venus is quickly destroyed by the extreme pressure, a spacecraft on Mars faces no such physical compression, though it must withstand freezing cold.

According to the passage, how does the atmospheric pressure on Venus compare to the atmospheric pressure on Mars?

The concept of urban heat islands is well-documented, but recent microclimatic research has shifted focus toward 'cool islands'—specifically, urban parks. While typical asphalt surfaces absorb solar radiation and radiate it as thermal energy, vegetated spaces mitigate this effect through evapotranspiration. During this process, plants absorb liquid water through their roots and release it as water vapor through microscopic leaf pores called stomata. Because this transition from liquid to gas consumes ambient heat energy, it directly lowers the local air temperature. However, the cooling efficiency of a park is not uniform; it is heavily influenced by the canopy density and the specific transpiration rates of the plant species present. Consequently, urban planners cannot simply add any green space to achieve optimal thermal reduction; they must select species whose physiological traits maximize vapor release.

According to the passage, why does the transition of water from a liquid to a gas lower the air temperature in a park?

The following passage is adapted from an article about ancient Greek acoustics. Match each paragraph of the passage to its primary main idea.

[Paragraph 1]
The ancient theater of Epidaurus, constructed in the fourth century BCE, is renowned for its extraordinary acoustics. Visitors standing at the center of the circular performance space, or orchestra, can whisper or tear a piece of paper, and the sound will be clearly heard by spectators sitting in the highest row of limestone seats, some sixty meters away. For decades, scientists and historians wondered whether this acoustic perfection was a result of deliberate design or merely a fortunate accident of geography.

[Paragraph 2]
Recent acoustic research has solved the mystery, revealing that the theater's limestone seats act as a sophisticated acoustic filter. Researchers discovered that the ridged rows of seats suppress low-frequency sounds��such as the rustle of wind or the murmurs of the audience—while reflecting high-frequency sounds from the stage. This filtering effect essentially amplifies the voices of actors and musicians, carrying their performances to the upper tiers of the theater.

[Paragraph 3]
However, this design does have a limitation. While the limestone seats are exceptionally good at transmitting high frequencies, they also suppress the lower frequencies of the actors' voices. To compensate for this loss, ancient actors relied on masks with built-in megaphones and projected their voices with specialized vocal techniques. Thus, the superb audibility was a combined achievement of architectural filtering and the performers' physical adjustments.

For decades, Ernst Mayr's Biological Species Concept (BSC) has stood as the cornerstone of evolutionary biology. According to the BSC, species are groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups. This definition shifts the focus of taxonomy away from morphological similarities and toward evolutionary processes, specifically the mechanisms that prevent gene flow. By defining species through reproductive isolation, the BSC provides a clear, process-oriented framework: speciation occurs when biological barriers to interbreeding evolve.

Yet, despite its conceptual elegance, the BSC is far from universally applicable. A major limitation is its restriction to sexually reproducing organisms, rendering it useless for the vast domain of asexual life, including bacteria, archaea, and many plants and fungi that reproduce clonally. Furthermore, the criterion of 'potential' interbreeding is notoriously difficult to test in practice, particularly when dealing with geographically separated (allopatric) populations or fossil specimens. In the fossil record, where genetic material is absent and reproductive behavior cannot be observed, paleontologists must rely on morphological differences to distinguish species, a method Mayr’s framework sought to supersede.

These limitations have prompted the development of alternative species concepts. The Phylogenetic Species Concept (PSC), for instance, defines a species as the smallest diagnosable cluster of individual organisms within which there is a parental pattern of ancestry and descent. Under the PSC, any population that possesses a unique, heritable physical or genetic trait is classified as a distinct species, regardless of whether it can interbreed with other populations. Proponents of the PSC argue that this approach is operational—it can be applied to asexual organisms and fossils alike—and that it more accurately reflects the historical branches of the tree of life.

The debate between supporters of the BSC and the PSC is not merely a semantic squabble over terminology; it reflects a fundamental divergence in research and pedagogical priorities. The BSC is primarily concerned with the mechanisms of evolutionary change—specifically, how reproductive barriers arise and maintain genomic integrity. For a population geneticist studying speciation in real-time, the BSC is an indispensable tool because it focuses on the very barriers that drive divergence. Conversely, the PSC is oriented toward cataloging biodiversity and reconstructing evolutionary history. Systematists and conservationists often favor the PSC because it is easier to apply to field data and museum specimens, and it tends to recognize more distinct lineages, which can have profound implications for environmental policy and conservation funding.

Ultimately, the quest for a single, all-encompassing species concept may be a misguided endeavor. Some modern biologists suggest a pluralistic approach, recognizing that different species concepts are useful for different subdisciplines of biology. Rather than viewing the BSC and PSC as mutually exclusive truths, they can be seen as complementary lenses: one focusing on the physiological and behavioral processes of isolation, the other on the historical patterns of lineage divergence. The ongoing debate highlights that species are not static, easily packaged units of nature, but dynamic evolutionary lineages whose definition depends heavily on the scientific questions being asked.

***

Which of the following best describes the primary purpose of the passage as a whole?

Passage

When Dr. Julian Thorne first looked at the ice core sample recovered from the Amundsen Sea, he was searching for the telltale ash layers of the 1815 Tambora eruption. However, the unexpected presence of micro-particles of cobalt at the deeper three-hundred-meter mark shifted his focus entirely. This depth corresponded to a period long before industrialization, suggesting an ancient cosmic impact event. To verify this, Julian sent an aliquot of the melted ice to the mass spectrometry lab in Denver. He had only been permitted to access these rare cores after securing the highly competitive polar research fellowship the previous autumn. Now, as he waited for the spectral readouts, Julian pulled up the digitized logbooks of the HMS Challenger from the late nineteenth century. Those early oceanographers had recorded strange, metallic sediment in their dredge buckets, a detail Julian had dismissed as contamination when he first read their reports during his graduate studies. The Denver lab’s automated notification chimed, interrupting his thoughts; the isotopic ratio of the cobalt was indeed non-terrestrial.

Based on the implicit chronological cues in the passage, arrange the following events in the order in which they occurred, from earliest to latest.

In the mid-nineteenth century, the pioneering methods of photography were defined by a sharp contrast between the daguerreotype, developed in France, and the calotype, developed in England. The daguerreotype created a single, incredibly sharp image directly on a silver-plated copper sheet. Because it lacked a negative, each print was entirely unique and could not be replicated, but it captured fine details with a clarity that amazed contemporaries. However, the process required toxic mercury vapors and resulted in delicate, fragile surfaces.

Conversely, the calotype process used paper negatives to produce positive prints. While the texture of the paper fibers made the final images look softer and less detailed than daguerreotypes, this method allowed for the creation of unlimited copies from a single negative. Consequently, while commercial portrait studios and scientific documentarians gravitated toward the precise realism of the daguerreotype, fine artists often preferred the calotype for its expressive, print-like qualities.

According to the passage, which of the following best describes how the practical and aesthetic qualities of the daguerreotype compared to those of the calotype?

The lead detective warned the team that any premature leak to the press would compromise the entire investigation. With several suspects still uncooperative and key forensic reports pending, absolute confidentiality was crucial to securing a conviction. The department could not afford a single mistake that might alert the target of their inquiry. Despite the intense pressure from local reporters demanding immediate updates, the officers remained silent, protecting their sources and ensuring that the delicate operation proceeded exactly as scheduled.

As used in the passage, the word *compromise* most nearly means which of the following?

Passage

Lord Roderick’s public disposition was marked by a fastidious, almost glacial rectitude that his contemporaries frequently mistook for arrogance, though it was in truth a protective armor forged during his youth. Yet, in the privacy of his estate, this austere veneer dissolved completely, exposing a temperament characterized by an almost pathological indecisiveness regarding even the most trivial domestic arrangements. While he could command an empire's fleet with resolute authority, he found himself utterly paralyzed when selecting the color of a library curtain or the scheduling of his daily rides. This paralyzing hesitation was not born of indifference, but rather of an agonizingly acute appreciation for the potential aesthetic disharmony of any choice he might make. To his butler, who observed these silent crises daily, Roderick’s internal state was not one of haughty detachment, but of a quiet, persistent vulnerability—a hypersensitivity to the external world that rendered him incapable of selecting a single course of action without mourning the options he was forced to abandon.

Question

According to the passage, Lord Roderick's behavior regarding minor domestic matters is characterized by which of the following traits?

Refracting telescopes and reflecting telescopes both gather light to magnify distant objects, but they do so using different optical components. A refracting telescope uses a curved glass lens at the front of a sealed tube to bend and focus light directly to the eyepiece. In contrast, a reflecting telescope uses a curved mirror at the bottom of an open tube to bounce light back up to a secondary mirror, which then directs it to the eyepiece. While refractors are highly durable and require little maintenance because of their sealed design, reflectors are generally cheaper to manufacture at larger sizes, making them more popular for viewing faint deep-space objects.

Based on the passage, how do refracting and reflecting telescopes primarily differ in their optical design and construction?

The following passage is adapted from an article exploring the ecological role of the North American beaver (*Castor canadensis*).

[Paragraph 1] (lines 1-12)
Beavers are widely recognized as ecosystem engineers due to their unique ability to manipulate their environment. By felling trees and constructing sturdy dams across streams, they systematically alter the hydrology of entire watersheds. The accumulation of water behind these structures transforms fast-flowing, narrow streams into expansive, slow-moving ponds and wetlands. These newly created aquatic zones dissipate the energy of flowing water, reducing downstream erosion and raising the local water table. Consequently, these structural modifications establish diverse, saturated habitats that support a wide variety of plant and animal species that could not otherwise survive in a standard riverine environment.

[Paragraph 2] (lines 13-24)
Beyond their physical impacts on landscape structure, beaver ponds function as highly efficient natural filtration systems. As sediment-laden water enters the slow-moving pool behind a dam, the drop in water velocity causes suspended particles to settle to the bottom. This process traps agricultural runoff, heavy metals, and excess nutrients like nitrogen and phosphorus, preventing them from traveling further downstream to sensitive estuaries. Furthermore, the saturated, low-oxygen conditions of the pond bottom slow the decomposition of organic matter, effectively sequestering carbon in the accumulated sediment. Over time, these chemical and biological processes significantly improve downstream water quality and contribute to carbon storage.

[Paragraph 3] (lines 25-37)
While the ecological benefits of beavers are extensive, their activities frequently clash with human development. The very dams that create beneficial wetlands can also flood adjacent agricultural fields, submerge roads, and damage residential properties. Historically, the standard response to these conflicts was the lethal removal of beavers and the demolition of their dams. However, modern conservation biology emphasizes non-lethal management techniques. Tools such as flow-control devices, which regulate pond depth without requiring dam destruction, and tree-wrapping protect infrastructure while preserving the invaluable ecological services that beaver-modified landscapes provide.

Match each section of the passage to its primary main idea.

When mid-twentieth-century classicists set out to translate Homeric epic for modern readers, they did not merely swap ancient Greek verbs for their English counterparts; they performed a silent act of cultural transplantation. To make the bronze-age warrior code palatable to a generation recovering from global conflict, translators frequently softened the raw, amoral ambition of Achilles, framing his rage not as an archaic social transgression, but as a modern, existential crisis. In doing so, they constructed a version of antiquity that mirrored their own era's search for individual meaning amidst collective ruin. This was not a failure of scholarship, but a demonstration of translation's true nature. A translation does not exist in a vacuum, nor does it serve as a static window to the past. Instead, it operates as a dynamic, historically situated dialogue. The translator is not a passive conduit, but an active participant who must negotiate between two distinct horizons of meaning. Consequently, every translation of a classic text says far less about the ancient world than it does about the historical moment in which the translator picks up the pen.

Which of the following statements best expresses the primary theme of the passage?

Historically, historians believed that the ancient Silk Road was solely a commercial highway for luxury goods like silk and spices. However, recent archaeological findings suggest that its most significant impact was actually the transmission of agricultural technologies.

Initially, excavations revealed that eastern crops, such as rice and peaches, began appearing in western markets much earlier than previously recorded. This discovery challenged the traditional view of the route as a simple merchant path, indicating a deeper ecological exchange. Furthermore, research showed that these crops did not just travel as cargo; instead, farming techniques and irrigation methods were systematically adopted by local communities along the route. Ultimately, this agricultural exchange permanently transformed the diets and farming landscapes of both East Asia and the Mediterranean, establishing the Silk Road as a catalyst for global environmental change rather than a mere trade route.

Based on the passage, what is the correct order of the steps of the author's central argument, from the initial premise to the final conclusion?

The emergence of French Impressionism in the late nineteenth century is frequently viewed as a sudden aesthetic rebellion, yet its development was deeply rooted in technological and cultural shifts. Prior to this period, artists mixed their pigments by hand in the studio, a laborious process that restricted painting primarily to indoor settings. The invention of the collapsible metal paint tube in 1841 fundamentally changed this dynamic. By preserving mixed oil paint and making it easily portable, the metal tube liberated artists from their studios, permitting them to paint directly outdoors. Simultaneously, the rapid commercialization of photography presented a profound challenge to traditional fine art. Because cameras could capture realistic detail with unmatched accuracy, painters felt increasingly freed from the historical obligation to serve as literal documentarians of reality. Instead of competing with the camera's precision, avant-garde artists turned their attention to capturing the transient, subjective effects of light and atmosphere. Consequently, this intersection of photographic realism and portable paint technology did not merely offer painters new options; it actively compelled them to redefine the medium, culminating in the spontaneous brushwork and vibrant, unblended color palettes that define the Impressionist aesthetic.

Based on the passage, the development of the Impressionist aesthetic was caused by which of the following relationships?

During the Song Dynasty in tenth-century China, the regional economy of Sichuan experienced a severe shortage of bronze coins, which were the standard medium of exchange. To facilitate trade, merchants began issuing private promissory notes printed on paper, known as *jiaozi*. These notes represented a value in copper currency and could be exchanged for metal coins at designated deposit houses. Recognizing the efficiency of this system in reducing the physical burden of transporting thousands of heavy coins across long distances, the Song government officially monopolized the production of *jiaozi* in 1024, establishing the world's first government-issued paper currency. This centralized system stabilized trade, although it eventually suffered from inflation due to excessive printing.

According to the passage, which of the following best describes the reason why the Song government officially took control of *jiaozi* production in 1024?

### Passage

The Underground Network of the Forest

For decades, traditional forestry viewed trees as solitary competitors engaged in a relentless struggle for sunlight, water, and soil nutrients. According to this classic Darwinian model, the strongest trees outgrow their neighbors, monopolizing resources and leaving weaker individuals to perish in the shade. However, recent developments in botanical research have revealed that this competitive view is incomplete. In reality, forest ecosystems are defined by cooperation, facilitated by vast underground networks of fungi that physically connect trees to one another. These networks, known as mycorrhizal networks, allow trees to share resources, communicate threats, and support the health of the entire forest community.

The partnership between trees and fungi is ancient, dating back over four hundred million years to the colonization of land by plants. These fungal threads, or hyphae, grow throughout the soil in an incredibly dense web of microscopic filaments. They wrap around or penetrate the outer cells of the root systems of trees. At the microscopic level, this connection forms a mutualistic relationship: the tree provides the fungus with carbon compounds produced through photosynthesis, while the fungus absorbs essential nutrients like phosphorus and nitrogen from the soil and delivers them to the tree. But the system is much larger than simple one-to-one exchanges. Individual fungal networks can span vast distances, linking multiple trees of the same species and even connecting entirely different species, such as paper birch and Douglas fir. Through these connections, the forest becomes an interconnected system.

One of the most remarkable functions of these mycorrhizal networks is the redistribution of vital resources. Researchers have demonstrated that carbon, water, and nitrogen can travel through fungal pathways from healthy, well-nourished trees to those in need. For example, a mature "mother tree" standing high in the canopy can channel carbon to young saplings growing in the deep forest understory, where sunlight is too scarce for sufficient photosynthesis. Without this supplemental nourishment delivered via the fungal network, many saplings would not survive their early years. This resource sharing represents an evolutionary strategy that preserves the integrity of the forest canopy, protecting the microclimate that benefits all resident species. Additionally, older trees that are dying will often pump their remaining carbon and nutrients back into the network, distributing their final resources to neighboring seedlings to help sustain the forest population for future generations.

In addition to resource sharing, connected trees utilize the fungal network to communicate about environmental threats. When a tree is attacked by herbivorous insects or infected by a pathogen, it can send biochemical warning signals through the mycorrhizal network to its neighbors. Upon receiving these signals, the neighboring trees immediately begin producing defensive compounds, such as tannin or volatile organic chemicals, to repel the impending pests. This early warning system allows the community of trees to mount collective defenses before the threat physically reaches them, significantly reducing the overall damage to the forest. Scientific experiments have traced these signals in real-time, showing that trees separated by yards of soil can react to a pest infestation on a single branch of a neighbor within hours of the initial attack.

Despite these cooperative functions, mycorrhizal networks also exhibit hierarchies that dictate resource distribution. The oldest and largest trees in a forest, often called hub trees, possess the most extensive root systems and the highest number of fungal connections. These hub trees act as central nodes in the network, regulating the flow of resources and information. If a hub tree is removed, either through logging or disease, the entire network can become fractured, severely compromising the forest's ability to recover from environmental disturbances.

Crucially, understanding the cooperative nature of these underground networks is essential for developing modern conservation strategies that protect entire ecosystems rather than isolated species. Historically, clear-cutting practices removed dominant trees while leaving younger ones behind, under the assumption that the remaining trees would grow faster without competition. However, we now know that removing these central hub trees disrupts the underground support network, leaving the remaining forest vulnerable to collapse. Modern forestry must shift toward practices that preserve these vital underground networks to ensure long-term ecological resilience.

In conclusion, the discovery of mycorrhizal networks has revolutionized our understanding of forest dynamics. Forests are not merely collections of individual trees competing for survival; they are complex, cooperative networks bound together by underground fungi. By recognizing the physical and chemical bonds that link trees, scientists and conservationists can better appreciate the intricate relationships that sustain terrestrial life, paving the way for more holistic and effective environmental stewardship.

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

In the mid-nineteenth century, the pioneering years of photography were defined by the rivalry between two distinct chemical processes: the daguerreotype and the calotype. Louis Daguerre’s method produced a single, highly detailed image on a sheet of copper plated with thin silver, which was developed using toxic mercury fumes. This technique created an image of remarkable clarity, yet its metallic surface made the photograph highly reflective and impossible to duplicate directly. In contrast, William Henry Fox Talbot’s calotype process utilized paper sensitized with silver compounds to generate a negative image. From this paper negative, multiple positive paper prints could be rendered. Although this capacity for replication gave the calotype a substantial advantage for commercial dissemination, the texture of the paper fibers inevitably absorbed and diffused the light, resulting in prints that lacked the sharp, minute details characteristic of the daguerreotype.

According to the passage, which of the following statements best describes an explicit contrast between the physical characteristics of a finished daguerreotype and a finished calotype?

While both the stick charts of the Marshall Islands and the portolan charts of medieval Europe served as indispensable guides for maritime navigation, they represented fundamentally different conceptions of space and navigation. Portolan charts, which appeared in the Mediterranean during the thirteenth century, were hand-drawn on parchment and mapped coastlines with mathematical precision, emphasizing fixed geographic grids, rhumb lines indicating wind directions, and stable landmarks. In contrast, Marshallese stick charts did not record fixed coordinates. Crafted from coconut fronds and shells, they were abstract mnemonic devices designed to illustrate the dynamic interaction of ocean swells, wave refraction patterns, and currents around low-lying atolls. While a European navigator relied on a portolan chart to plot a static course from one visible landmark to another across open waters, a Marshallese navigator used stick charts as mental frameworks to sense the boat's motion relative to invisible ocean currents, storing the charts on land rather than consulting them at sea.

Based on the passage, which of the following statements best describes the primary difference in how navigators used portolan charts compared to how they used Marshallese stick charts?

The Choruses of the Canopy: Songbirds and the Science of Speech

For centuries, human beings have been captivated by the complex, melodic songs of birds. To the casual listener, these melodies are simply beautiful sounds of nature. To neurobiologists and linguists, however, the song of a sparrow or a zebra finch is a window into one of the most complex cognitive processes in the animal kingdom: vocal learning. Vocal learning is the ability to acquire, modify, and produce vocalizations based on auditory experience. While many animals communicate using sounds, very few possess this specific ability. Most species, including dogs, cats, and even our closest primate relatives, rely on innate vocalizations that are genetically hardwired and do not require tutoring to develop. Humans are vocal learners, and among non-human animals, songbirds are the most prominent and accessible subjects for studying this rare trait.

The neural architecture that enables songbirds to sing is remarkably specialized. Unlike species with simple vocalizations, songbirds have a complex network of interconnected brain areas known as the 'song system.' This system is divided into two primary neural pathways: the motor pathway and the anterior forebrain pathway. The motor pathway, which includes regions like the HVC (high vocal center) and the robust nucleus of the arcopallium (RA), is responsible for the physical production of song. The anterior forebrain pathway, on the other hand, is crucial for song learning and social transmission. What fascinates scientists is that these brain regions share striking functional and structural similarities with the speech areas in the human brain, such as Broca's area. This convergent evolution suggests that nature has solved the challenge of vocal learning using similar neural designs across vastly different species.

To understand how a young songbird learns its song, researchers study their development in stages that mirror human language acquisition. The process begins with the sensory phase, during which a young bird—usually a male—listens to and memorizes the song of an adult 'tutor,' typically its father. During this time, the chick does not sing; it simply absorbs the acoustic properties of the song, creating an internal neural template. This critical period is highly time-sensitive; if a young bird is isolated from adult tutors during this window, it will never develop a normal, species-typical song. Next comes the sensorimotor phase, which is equivalent to human babbling. The young bird begins to produce quiet, unstructured sounds called 'subsong.' As it practices, it continuously compares its own vocal output with the stored memory of the tutor's song, using auditory feedback to adjust its performance. Over weeks of trial and error, the song crystallizes into a precise, stable adult song that the bird will use for the rest of its life to attract mates and defend territory.

Because of these behavioral and neural parallels, songbirds have become invaluable model organisms for biomedical research. By studying how birds acquire and maintain their songs, scientists can investigate the genetic and cellular mechanisms underlying human speech disorders, such as stuttering or the speech difficulties associated with autism spectrum disorder. For instance, researchers have identified specific genes, like FOXP2 (often dubbed the 'language gene'), that play critical roles in both human speech development and songbird vocal learning. Mutations in FOXP2 lead to severe speech impairments in humans, and when scientists alter this gene in songbirds, the birds' ability to learn songs is similarly disrupted.

Ultimately, the study of songbirds reminds us that the division between human language and animal communication is not as wide as once believed. By exploring the avian brain, researchers are not only uncovering the secrets of how birds sing but also gaining profound insights into the biological foundations of human language itself.

The passage as a whole is best described as an effort to perform which of the following functions?

Early cartography is frequently evaluated through the lens of progressive accuracy, a teleological narrative wherein each century’s mapmakers are seen as merely correcting the geographical errors of their predecessors. Under this paradigm, a sixteenth-century chart of the Atlantic is judged primarily by how closely its coastlines conform to modern satellite telemetry. Yet this retrospective calibration overlooks the cognitive landscape of the era. Renaissance mapmakers did not view space as a value-neutral coordinate grid to be measured with absolute geometric precision; rather, they constructed space as a canvas of geopolitical claims, theological order, and symbolic narratives. The inclusion of elaborate sea monsters or imaginary islands was not a failure of empirical rigor, but a deliberate codification of cultural anxieties and imperial assertions. By imposing contemporary standards of cartographic literalism onto historical artifacts, modern observers fail to decode the maps' actual communicative functions. Early maps were never meant to be objective mirrors of physical space, but rather active instruments of political and spiritual alignment, representing the world not as it was measured, but as it was imagined and contested.

Which of the following best states the central argument implied by the author of the passage?

Although the committee had expressed deep reservations about the proposed urban redevelopment initiative, the lead architect remained optimistic. She argued that the integration of green spaces would revitalize the historic district, drawing tourists and boosting local commerce. However, the preservationists in the community worked tirelessly to check the rapid progress of the developers, claiming that the historical integrity of the neighborhood was at risk. They argued that once the old structures were demolished, the unique character of the area would be lost forever, regardless of how many parks were built in their place.

As used in the passage, which of the following is the closest meaning of the word 'check'?