Main Ideas and Themes

The passage below is adapted from an essay about the history of museums:

Line Passage
1 In the mid-nineteenth century, public museums underwent a significant
2 transformation in how they displayed their collections. Previously, these
3 institutions functioned primarily as "cabinets of curiosities," where private
4 collectors crammed unrelated artifacts, fossils, and artwork into single rooms
5 with little order. However, as public funding increased, curators began to
6 organize objects chronologically and by geographic origin. This shift was
7 intended to educate the general public rather than merely entertain wealthy
8 patrons, turning museums into structured spaces of learning.
9
10 A key figure in this transformation was Christian Jürgensen Thomsen, who
11 organized the Royal Museum of Nordic Antiquities in Copenhagen. By dividing
12 artifacts into the Stone, Bronze, and Iron Ages, Thomsen established the
13 three-age system of archaeology. This system was not just a convenient storage
14 method; it provided a visual timeline of human technological progress, allowing
15 visitors to comprehend historical evolution at a glance. Thomsen's method was
16 soon adopted across Europe, permanently altering the field of public museum
17 exhibitions.

Based on the passage, which of the following statements best describes the main idea of Paragraph 2 (lines 10-17)?

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?

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?

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)?

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.

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.

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?

In modern urban planning, the concept of the 'pocket park'—a small public green space tucked into a single vacant lot or nestled between towering brick buildings—has gained significant traction. Proponents frequently argue that these tiny sanctuaries are vital for improving the mental health of city dwellers, who often suffer from 'nature deficit' in dense concrete environments. For instance, a recent study in Philadelphia showed that residents living within a five-minute walk of a pocket park reported significantly lower stress levels and higher overall life satisfaction. Additionally, environmental scientists point out that pocket parks can help mitigate the urban heat island effect by replacing heat-absorbing asphalt with cooling grass and trees, while also providing minor stormwater runoff control during heavy summer downpours. However, urban sociologist Dr. Clara Vance argues that the ultimate significance of pocket parks lies not in these localized ecological benefits or individual wellness improvements, but in their capacity to foster community cohesion. By serving as informal gathering spaces, these small parks transform anonymous urban blocks into active, socially integrated neighborhoods where diverse residents regularly interact and build mutual social trust.

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

The following passage explores the scientific discoveries surrounding the Earth's deep biosphere.

### Passage

For decades, biological science operated under a fundamental assumption: life is a surface phenomenon, bound to the thin sliver of the Earth's crust that receives sunlight. This view was not without merit, as the vast majority of known ecosystems rely on photosynthesis, the process by which green plants and algae convert solar radiation into chemical energy. However, recent deep-drilling projects into the subsurface of both continents and the ocean floor have shattered this dogma. Scientists have revealed a vast, subterranean realm teeming with microscopic life, a domain now known as the deep biosphere. Thriving miles below our feet under crushing pressures and scorching temperatures, this hidden world represents a significant fraction of Earth's total biomass. The discovery of the deep biosphere fundamentally redefines the ecological limits of life, showing that biological activity does not require solar energy to persist. Ultimately, the exploration of this deep biosphere reveals that life is not a fragile surface phenomenon, but rather an intrinsic, rock-powered geological force that penetrates deep into the planetary crust and expands our search for habitable worlds.

In these deep subterranean environments, the absolute absence of sunlight precludes photosynthesis, forcing organisms to adopt alternative metabolic pathways to survive. Rather than consuming organic matter produced by surface plants, deep-subsurface microbes rely on chemolithoautotrophy—a process by which organisms synthesize organic compounds using energy derived from the oxidation of inorganic substances. The geological crust of the Earth provides a rich menu of such substances, including hydrogen, iron, and sulfur. For instance, when water reacts with iron-rich rocks at high temperatures—a process known as serpentinization—it releases molecular hydrogen. Subsurface microbes capture this hydrogen and combine it with carbon dioxide to produce methane, yielding enough energy to sustain their metabolic functions. Another source of energy is radiolysis, where radiation from radioactive isotopes in the crust splits water molecules into hydrogen and oxygen. This rock-powered biology operates completely independently of the surface world, demonstrating that geological processes alone can generate the energy required to support active, self-sustaining ecosystems.

Beyond altering our understanding of ecology, the deep biosphere offers profound insights into the history of life on Earth. The surface of our planet has been subjected to cataclysmic events throughout geological time, from devastating asteroid impacts to global glaciations that periodically encased the oceans in ice. While these events triggered mass extinctions on the surface, the deep subsurface remained shielded from atmospheric volatility, providing a stable sanctuary for billions of years. Genetic sequencing of subterranean microbes supports this view, revealing that many of these organisms belong to ancient, slow-evolving branches near the root of the tree of life. Consequently, many evolutionary biologists now hypothesize that life did not originate in shallow tide pools, as Charles Darwin famously suggested, but rather in the deep, protected recesses of the Earth's crust, where geothermal heat and chemical gradients provided the perfect crucible for early biochemistry. Under this view, the subsurface was not a destination to which surface organisms retreated, but rather the cradle from which they eventually emerged.

This paradigm shift has profound implications for astrobiology, the study of the origin, evolution, and distribution of life in the universe. Historically, the search for extraterrestrial life has focused on finding planets within the 'Goldilocks zone'—the narrow orbital band where a planet's surface temperature allows for liquid water. However, the realization that Earth hosts a massive subsurface biosphere suggests that planetary habitability is not restricted to the surface. Celestial bodies previously deemed hostile, such as Mars or the icy moons of Jupiter and Saturn, may possess active geothermal subsurface environments. For example, Europa and Enceladus harbor liquid oceans beneath miles of ice, where hydrothermal activity could mimic the conditions that support Earth's deep microbes. By demonstrating that life can flourish in the deep crust without sunlight or atmospheric oxygen, the deep biosphere expands the habitable zones of other planets, shifting the search for extraterrestrial life from surface observations to subsurface exploration. Consequently, astrobiologists are designing missions equipped to drill into alien soils, recognizing that the signs of cosmic life are likely buried far beneath their surfaces.

### Question

Match each numbered paragraph of the passage to the statement that accurately represents its explicitly stated sub-main idea.

The following passage is adapted from an essay on the history of astrobiology and subsurface ecology:

For decades, biology textbooks defined the biosphere as a thin, sunlit envelope clinging to Earth's surface, where photosynthesis fueled virtually all ecological chains. This surface-centric view began to fracture in the late twentieth century with the discovery of microbes living miles beneath the seafloor and deep within continental basalt. These subsurface organisms, collectively termed the 'deep biosphere,' operate in complete darkness under crushing pressures, drawing energy not from sunlight but from chemolithoautotrophy—the chemical weathering of rocks and radioactive decay. While initial discoveries were dismissed as surface contamination, subsequent sterile drilling initiatives confirmed that these deep-dwelling prokaryotes constitute a massive fraction of Earth's total biomass. However, the significance of the deep biosphere extends beyond mere numbers or exotic metabolic pathways. It challenges our understanding of the conditions necessary for life, suggesting that planetary habitability is not solely determined by stellar proximity or surface water. Instead, the interior of a planet, long considered inert, may serve as a primary incubator of life, rendering geothermal activity far more critical than solar radiation in astrobiological models. Consequently, the search for extraterrestrial life has shifted from a preoccupation with surface liquid water to the investigation of sub-surface heat and chemistry.

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

For decades, early epigraphers studying Mesoamerican ruins assumed that the oldest writing systems in the region, such as the Zapotec glyphs dating to 500 BCE, served a primarily economic function—tracking agricultural yields and tributes. This hypothesis was bolstered by the prominent depiction of calendar dates and numerical counts alongside the glyphs. However, recent comprehensive analyses of monuments across the Oaxaca Valley paint a vastly different picture. While agricultural cycles and tributary lists are indeed recorded in minor, peripheral inscriptions on ceramic vessels, the grand stone monuments themselves—monolithic structures known as *danzantes*—were erected almost exclusively to legitimize the political authority of ruling elites during periods of intense warfare. These stone inscriptions record military conquests, the capture of rival lords, and the divine lineage of kings, using calendar dates not to coordinate harvests, but to anchor royal accessions and campaigns to auspicious astronomical alignments. Thus, the monumental writing was less an administrative ledger and more a tool of statecraft and elite propaganda, designed to project power outward to subordinate communities and inward to rivals. The focus on economic transactions in early scholarship arose from an over-reliance on portable artifacts, obscuring the ideological work performed by Zapotec public monumentality.

Which of the following statements best summarizes the author's primary argument regarding the function of early Zapotec monumental writing?

Adapted from an essay examining the intersection of art and material science in Europe, the paragraph below discusses the impact of synthetic pigments.

Paragraph 2 (lines 15–32)
Before the accidental synthesis of Prussian blue in 1706 by Berlin colorist Heinrich Diesbach, artists had to rely on ultramarine—a luxurious pigment ground from lapis lazuli imported from the remote mines of Afghanistan—for their deepest blues. Ultramarine was so prohibitively expensive that patrons often specified its quantity in contracts, reserving its use for the robes of the Virgin Mary or other central figures to signal piety and wealth. By providing a chemically stable, highly saturated alternative at a fraction of the cost, Prussian blue democratized the color blue, instantly altering the economics of European painting. However, the pigment did more than shift market dynamics; its rapid adoption by painters across the continent sparked a structural revolution in palette design. For the first time, artists could mix deep blues with a variety of yellow and white pigments to produce subtle, lightfast greens and purples, prompting a departure from the stark, color-blocked compositions of the Renaissance toward the fluid, atmospheric landscapes of the Rococo and early Romantic eras.

Which of the following statements best captures the central point of Paragraph 2 (lines 15–32)?

The following passage is adapted from an essay about desert ecology and plant survival strategies.

Paragraph 3 (lines 15–28)
In the arid expanse of the Sonoran Desert, seedling survival is a precarious venture, with young cacti frequently succumbing to intense solar radiation and foraging herbivores. However, a biological phenomenon known as 'nurse parenting' dramatically alters these odds. Mature desert trees, such as the foothill paloverde, serve as vital protectors for vulnerable saguaro seedlings. By establishing themselves beneath the dense canopy of a paloverde, saguaro seedlings are shielded from the scorching midday sun, which significantly reduces soil temperature and moisture loss. Furthermore, the physical barrier of the host tree's low-hanging branches deters large herbivores like jackrabbits from grazing on the tender young cacti. Over decades, as the saguaro grows and develops a robust root system, it eventually outcompetes its host tree for water and nutrients, sometimes leading to the paloverde's demise, but the initial phase of their relationship remains a crucial cornerstone of desert regeneration.

Which of the following statements best expresses the main idea of Paragraph 3?

### Passage

Historically, the literary translator was often viewed as a transparent pane of glass—an invisible medium through which a text could pass from one language to another without alteration. This passive conception of translation underpins the traditional, yet highly flawed, view that the primary measure of a translation's success is its literal fidelity to the original. Under this model, any intervention by the translator is seen as a contamination, an infidelity to the author’s singular voice. However, this perspective overlooks the profound cultural and linguistic negotiations that occur whenever text crosses national boundaries. In reality, literary translation is not merely a technical exercise in linguistic substitution, but a transformative act of cultural mediation that shapes—and sometimes distorts—how a source text is received and understood globally.

To understand the active agency of the translator, one must examine the fundamental differences between languages. Languages are not simple systems of corresponding nomenclature; they are repositories of cultural memory, idiomatic nuance, and historical experience. A word in one language rarely has a perfect semantic twin in another. For instance, the German concept of *Waldeinsamkeit*—the feeling of being alone in the woods and connected to nature—cannot be rendered in English by a single equivalent term without losing its poetic resonance. When a translator encounters such untranslatable concepts, they must make an active choice: whether to prioritize literal accuracy at the expense of aesthetic beauty, or to preserve the emotional impact by altering the literal text. In making these decisions, the translator ceases to be a passive vessel and instead becomes an active co-creator of the literary work.

This co-creative power is particularly visible in the history of translating classical epics. Consider the various English translations of Homer’s *Iliad*. In the eighteenth century, Alexander Pope translated the epic into heroic couplets, adapting the ancient Greek verse to fit the neoclassic tastes of his contemporary British readers. Pope’s translation was wildly popular, but it presented an *Iliad* that sounded more like a polite drawing-room debate than a gritty, bronze-age war. In contrast, twentieth-century translations, such as those by Richmond Lattimore or Robert Fagles, sought to capture the rugged, oral formulaic nature of Homer’s original Greek. Neither approach is objectively "correct" or "incorrect"; rather, each translator constructed a distinct version of Homer that served the cultural needs of their respective eras. These translations demonstrate that the target language’s cultural expectations dictate the shape of the translated text just as much as the source text itself.

Moreover, the impact of translation extends far beyond aesthetic considerations; it plays a critical role in the geopolitical dynamics of world literature. The selection of which texts are translated, and how they are framed, is deeply bound up with questions of power and cultural dominance. Historically, works from marginalized cultures have often been translated into major global languages like English or French only after undergoing significant domestication—a process by which the foreign elements of a text are smoothed over to make it more palatable to Western readers. This selective adaptation can result in a skewed representation of the source culture, reinforcing pre-existing stereotypes rather than challenging them. By contrast, a translation strategy that retains foreign syntax and cultural references—a method known as "foreignization"—can force readers to confront the alterity of the text, thereby disrupting the linguistic hegemony of the target culture.

Thus, the choices made by a translator are inherently political and cultural. Whether choosing to domesticate or foreignize, to emphasize literal fidelity or stylistic resonance, the translator acts as a gatekeeper of cross-cultural understanding. To read a translated work is to participate in a dual authorship: one that belongs to the original creator, and another that belongs to the translator who rebuilt that world in a different tongue. By recognizing translation as an active, interpretive art rather than a mechanical science, we can begin to appreciate the complex negotiations that define global literature. The translator does not simply hold up a mirror to the original work; they paint it anew, and in doing so, determine the very parameters of its global existence.

Based on the passage, the statement that literary translation is a transformative act of cultural mediation that shapes global reception, rather than a mere mechanical word-for-word substitution, is accurate.

### Passage

In the early twentieth century, gray wolves (*Canis lupus*) were systematically eliminated from Yellowstone National Park due to predator control programs. By the 1920s, the park’s wolf population was completely eradicated, leaving the ecosystem without its primary apex predator. For decades, scientists and park managers observed a gradual decline in the health of Yellowstone’s valleys, though the precise cause remained a subject of intense debate. It was not until the landmark reintroduction of gray wolves in 1995 that the full ecological significance of the species became clear. The reintroduction of gray wolves to Yellowstone National Park has proved that restoring a top predator can completely reshape and revitalize an entire ecosystem through a cascade of ecological changes. This phenomenon, known to ecologists as a trophic cascade, demonstrates how influence at the top of the food chain trickles down to affect every level of the environment.

With the wolves absent for seventy years, the population of elk (*Cervus canadensis*), the wolves' primary prey, had exploded. Unchecked by predators, large herds of elk gathered along river valleys, heavily browsing on young woody plants. This constant grazing prevented trees such as willows, aspens, and cottonwoods from growing beyond seedling height. The valleys became barren, and the lack of shade and young timber threatened other wildlife. However, the return of the wolves quickly disrupted this pattern. By reducing and dispersing the elk populations, wolves allowed overbrowsed streamside vegetation like willows and aspens to regenerate. As wolves hunted, elk were forced to move more frequently and avoid open valleys where they were vulnerable. Consequently, the vegetation in these valleys began to recover, growing several meters high in just a few years.

This botanical recovery initiated a surprising change in the physical landscape of the park. When the streamside trees and shrubs were stunted by elk, their shallow roots could not hold the soil in place. As a result, riverbanks rapidly eroded, causing streams to become wider, shallower, and muddy. Once the wolves returned and the vegetation recovered, the plants' growing root systems bound the soil along the water's edge. The regrowth of trees stabilized riverbanks and altered the physical geography of Yellowstone's waterways by reducing erosion. Rivers began to run cleaner and established more stable, meandering paths. Deep pools formed, creating critical microhabitats for aquatic life. Thus, the presence of a predator indirectly reshaped the very paths of the rivers.

The recovery of the forests and rivers in turn sparked a chain reaction among Yellowstone’s animal communities. The rejuvenated willow and aspen trees provided essential building materials and food for North American beavers (*Castor canadensis*), which had nearly vanished from the park's streams. Beavers returned in large numbers, building dams that created deep, cool ponds. These ponds became habitats for fish, frogs, and waterfowl. Additionally, the taller trees offered nesting sites for migratory birds, leading to a rise in bird diversity. The resurgence of vegetation and wolf-provided carrion created new habitats and food sources, boosting populations of beavers, birds, and other carnivores. Scavengers such as grizzly bears, bald eagles, and ravens also benefited from the remains of wolf kills, particularly during harsh winters when food was otherwise scarce.

Today, Yellowstone stands as a premier example of ecological restoration. The return of the gray wolf has shown that an ecosystem is not merely a collection of isolated species, but a complex, interconnected web where the loss or restoration of a single key player can have profound effects. While the reintroduction initially faced skepticism from local ranchers and communities, the scientific data gathered over the past three decades has solidified the project’s success. It serves as a powerful model for conservation efforts worldwide, proving that active restoration of trophic levels is a viable strategy for repairing damaged landscapes.

### Question
Based on the passage, match each of the specified paragraphs to its explicitly stated main or sub-main idea.

In December 1938, Marjorie Courtenay-Latimer, a museum curator in South Africa, was inspecting the catch of a local fishing trawler when she noticed an unusual blue fish. The specimen, with its limb-like lobed fins and heavy scales, did not match any modern fish species she had ever seen. Courtenay-Latimer sent a sketch to chemist and amateur ichthyologist J.L.B. Smith, who recognized it as a coelacanth—a primitive fish previously believed to have gone extinct 66 million years ago. This discovery shocked the scientific community, as it challenged established timelines of evolutionary history and provided a living link to the prehistoric past. Over the next several decades, researchers successfully located living populations of coelacanths in deep marine canyons off the coast of East Africa and Indonesia, allowing scientists to study their unique physiology in their natural environment. While early search efforts were slow and costly, modern submersible technology has made observing these elusive "living fossils" much more feasible. Today, the coelacanth serves as a powerful reminder of how much of the deep ocean remains unexplored.

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

For centuries, historians treated historical maps primarily as objective, literal records of geographical knowledge, analyzing them to trace the accuracy of exploration or the expansion of empires. However, a major shift occurred in the late twentieth century, pioneered by cartographic theorists who argued that maps are never completely neutral representations of reality. Instead, these scholars proposed that maps are socially constructed texts that reflect the biases, political agendas, and cultural values of the societies that produced them. For instance, a seventeenth-century European map might deliberately exaggerate the size of a colonial outpost to project power, or omit indigenous settlements entirely to justify land acquisition. While early historians focused on detecting the mathematical precision of coordinates and coastlines, modern analysis prioritizes decoding these hidden ideological statements. By examining what is left off a map, as well as what is included, researchers can uncover the power dynamics of past eras, transforming our understanding of cartography from a history of science to a history of cultural rhetoric.

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

The following passage is adapted from an article about the ecology of tropical rainforests.

Paragraph 1 (lines 1–11)
Rainforests are famous for their rich biodiversity, housing more than half of the world's plant and animal species within a complex, multi-layered structure. From the dark forest floor to the sun-drenched emergent layer, each level of the forest supports unique ecological communities that have adapted to specific microclimates. Understanding how these layers interact is essential for conservationists trying to preserve these delicate ecosystems.

Paragraph 2 (lines 12–25)
The rainforest canopy, which forms a dense ceiling of leaves and branches approximately 100 feet above the ground, acts as the primary regulator of the forest's internal climate. By intercepting up to 90 percent of incoming sunlight, the canopy prevents the forest floor from drying out, maintaining the high humidity and stable temperatures crucial for understory species. Additionally, this leafy barrier buffers the lower levels from the destructive force of heavy tropical rains, slowing the descent of water and preventing soil erosion. Consequently, the canopy serves as a protective shield that stabilizes the environment below it.

Which of the following statements best summarizes the main idea of Paragraph 2 (lines 12–25)?

The following passage describes bioluminescent signaling in certain marine organisms:

In the twilight depths of the Caribbean Sea, certain species of tiny, shelled crustaceans known as ostracods engage in a nocturnal ritual of remarkable complexity. Unlike most bioluminescent organisms, which emit light primarily to startle predators or lure prey, these male ostracods release precise, pulsing sequences of blue light into the water column. These luminous trains, lasting only a few seconds, serve as highly specific courtship signals designed to attract females of the same species. By varying the duration of the pulses, the distance between successive emissions, and the overall trajectory of the swimming path, different ostracod species are able to occupy the same geographic space without cross-species mating errors. While researchers have documented that these displays are energetically costly and increase vulnerability to visual predators like reef fish, the evolutionary pressure to secure a mate has favored the preservation of these elaborate signaling systems. Indeed, this specialized behavior represents one of the few confirmed instances of complex visual signaling in the deep ocean, illustrating how sexual selection can drive physiological and behavioral adaptations that seemingly contradict basic survival strategies.

Which of the following statements best summarizes the main idea of the passage as a whole?