Critical Reasoning

Analysis of fossilized tooth enamel from *Gigantopithecus*, a giant primate that inhabited Southeast Asia during the Pleistocene epoch, revealed consistently low carbon-13 isotope ratios across late Pleistocene specimens. In mammalian herbivores, low carbon-13 ratios reflect a diet dominated by $C_3$ foliage from dense forest canopies, whereas elevated carbon-13 ratios indicate consumption of $C_4$ grasses typical of open savannahs. Because regional climate records show that open grasslands expanded significantly while dense forests shrank during this period, researchers concluded that *Gigantopithecus* went extinct primarily because its rigid dietary dependence on deep-forest $C_3$ vegetation prevented it from adapting to expanding grassland habitats.

Which of the following, if true, most seriously weakens the researchers' argument?

Archaeologists analyzing a 4th-century BCE Mediterranean shipwreck discovered that all preserved ceramic transport amphorae contained interior traces of pinaceous resin, a substance traditionally used to seal vessel walls against liquid seepage. Because pinaceous resin was significantly more expensive than clay-based sealant alternatives during this era, researchers concluded that the ship's cargo consisted exclusively of high-value luxury wines intended for wealthy buyers, rather than common staples like fish sauce or olive oil. Which of the following, if true, most seriously weakens the researchers' conclusion?

Recent spectrographic analyses of upper Paleolithic cave paintings in the Cantabrian region reveal that the sophisticated use of charcoal shading previously attributed to deliberate artistic chiaroscuro was, in fact, the unintended byproduct of periodic torchlight exposure during subsequent ritual occupancy. Art historians have long maintained that these late Solutrean artists possessed an advanced, intuitive grasp of three-dimensional perspective, citing the graded carbon deposits along natural rock contours as evidence of intentional modeling. However, carbon-14 dating of the pigment layers demonstrates that the main charcoal deposits postdate the initial mineral-pigment outlines by several centuries. Consequently, scholars must abandon the assumption that these subterranean compositions represent an early culmination of visual realism, recognizing instead that their visual depth is largely an accretive historical artifact.

Based on the passage, which of the following statements express main conclusions or core claims advocated by the author? Select all that apply.

Dendrochronological analysis of 14th-century oak timber beams extracted from agricultural granaries across Northern Europe demonstrates a pronounced, three-decade narrowing of annual growth rings between 1315 and 1345. Historians argue that this growth contraction indicates a severe, region-wide prolonged drought during those decades, which directly triggered the widespread grain harvest failures and subsequent famines recorded in monastic chronicles of the era.

Which of the following is an assumption on which the historians' argument depends?

A technology firm recently deployed an automated AI-driven customer support chatbot to resolve routine user inquiries. After three months of deployment, the firm reported a 25 percent decrease in total customer service operating expenditures and concluded that the implementation of the chatbot directly caused this reduction in costs. Which of the following, if true, provides the strongest support for the firm's conclusion?

Glaciologists investigating subglacial lakes in Antarctica long posited that the extreme hydrostatic pressure and total darkness of these environments would prevent any significant biological activity within subglacial sediment layers. However, recent genomic sequencing of core samples retrieved from Lake Mercer revealed flourishing communities of chemolithoautotrophic bacteria that metabolize iron and sulfur compounds derived from subglacial bedrock weathering. Because these microbial ecosystems thrive independently of solar energy and atmospheric carbon exchange, researchers initially asserted that subglacial lakes represent completely isolated biological reservoirs preserved since the ice sheet's formation. Nevertheless, isotopic tracing of subglacial water flow has recently demonstrated periodic hydraulic flushing between adjacent subglacial basins, indicating that subglacial microbial habitats are neither stagnant nor ecologically isolated, but rather form an interconnected continent-wide hydrological network.

Which of the following statements express main conclusions or claims advocated by the author of the passage? Select all that apply.

A boutique coffee roaster introduced a new line of dark roast coffee beans last month. During that same month, total customer traffic and overall sales at the store increased by 25 percent. The store owner concluded that the new dark roast line was directly responsible for the boost in sales. Which of the following best describes the flaw in the store owner's reasoning?

To reduce peak summer energy demand, municipal planners in Ardenton mandated high-albedo reflective roof coatings for all commercial warehouses. In trial runs, warehouses with these coatings experienced a 20 percent drop in interior roof-level temperatures, leading to a 15 percent decrease in air-conditioning energy consumption. City officials now conclude that extending this mandate to all single-family residential homes will achieve a similar 15 percent reduction in total residential cooling energy consumption during summer months.

Which of the following, if true, most seriously weakens the city officials' conclusion?

Archaeobotanical excavations at the high-altitude Andean settlement of Qullpa revealed a dramatic increase in charred cultivated quinoa seeds in soil strata dating to approximately 1000 CE, alongside a marked decrease in recovered wild game bones from the same layer. Paleoclimatic data indicate that the region experienced a prolonged drought beginning around 1000 CE. Researchers conclude that this climate shift forced the inhabitants of Qullpa to abandon their previously balanced hunting-and-gathering subsistence strategy in favor of intensive quinoa cultivation. Which of the following is an assumption on which the researchers' conclusion depends?

Palynologists studying Holocene sediment cores in the Pacific Northwest have long attributed the dramatic post-glacial expansion of Douglas fir forests primarily to warming temperatures and increased precipitation. However, recent high-resolution charcoal micro-stratigraphy reveals that peak Douglas fir expansion coincided precisely with a sharp increase in low-intensity fire frequency, while climate proxies during this exact period indicate relative hydrological stability. Furthermore, experimental burns in modern old-growth stands demonstrate that periodic surface fires suppress competing shade-tolerant hardwoods without damaging thick-barked Douglas fir saplings. Consequently, researchers must revise the conventional climate-driven model and recognize that anthropogenic or natural fire regimes, rather than shifting macroclimatic trends, were the primary catalyst for the historical dominance of Douglas fir across the region.

Which of the following best expresses the main conclusion of the argument?

To combat outbreaks of multi-drug resistant Acinetobacter baumannii in intensive care units, a regional health network replaced all alcohol-based hand rubs with an advanced chlorhexidine-glucoheptonate formulation. Over the subsequent twelve-month period, hospital-acquired A. baumannii infection rates in these units dropped by 45 percent. Concluding that the new formulation was directly responsible for this reduction, the network's epidemiological board mandated its exclusive use across all patient departments to suppress hospital-acquired bacterial infections. Which of the following, if true, most seriously undermines the epidemiological board's conclusion?

In 2023, a regional public health agency launched a free municipal exercise program aimed at reducing overall rates of physical injury among senior citizens. By the end of the year, official data showed that seniors who regularly participated in the program experienced a significantly lower rate of home fall injuries compared to non-participants. Surprisingly, however, total emergency room visits for injuries among participating seniors increased by 15 percent over the same period.

Which of the following statements, if true, help to resolve the apparent discrepancy described above? Select all that apply.

A metropolitan transit authority plans to transition its entire heavy maintenance fleet from conventional diesel to synthetic electro-fuel produced via direct-air carbon capture and electrolysis powered by a newly constructed offshore wind farm. The authority's financial and environmental model asserts that this transition will achieve net-zero carbon emissions across all maintenance operations within two years while maintaining total municipal fleet operational expenditures at or below current levels.

Which of the following statements represent underlying assumptions upon which the transit authority's argument depends? Select all that apply.

Archaeologists studying Neolithic settlements in the Scandinavian archipelago recently argued that the introduction of copper tool working around 2500 BCE caused a dramatic surge in localized timber harvesting for smelting fuel. This conclusion rests on sediment cores retrieved from lakes adjacent to early copper smelting hearths, which exhibit a sudden, marked reduction in tree pollen dating to the exact era when copper artifacts first appear in the region. Which of the following, if true, most seriously weakens the archaeologists' argument?

For decades, bioacousticians assumed that the specialized ultrasonic vocalizations of neotropical leaf-nosed bats evolved primarily to evade predation by nocturnal raptors. However, recent echolocation recordings and dietary analyses indicate that these high-frequency calls attenuate rapidly in dense rainforest foliage, rendering them ineffective for long-range threat detection. Instead, the signals match the resonant frequencies of specific night-blooming epiphytes, enabling the bats to navigate intricate floral corridors and optimize foraging efficiency. Furthermore, genetic sequencing reveals that the divergence of these acoustic traits coincided precisely with the evolutionary radiation of epiphytic angiosperms in the Neotropics. Consequently, predator avoidance was not the driving evolutionary pressure for high-frequency call adaptation; rather, mutualistic plant-pollinator coevolution shaped the acoustic specialization of these Chiroptera lineages.

Which of the following statements express main claims or central conclusions established by the argument? Select all that apply.

Public health officials recently claimed that a new vaccination campaign led directly to a 20 percent decrease in seasonal influenza cases this winter. However, data from regional health clinics indicate that the reduction in flu cases occurred almost entirely in counties where strict sanitation protocols were introduced simultaneously. While vaccinations certainly provide individual protection against virus strains, the dramatic overall drop in transmission was primarily driven by improved hygiene practices rather than the vaccine rollout itself.

Which of the following best describes the roles played by the two boldfaced portions in the argument above?

To reduce particulate matter emissions in its central historic district, municipal administrators implemented a initiative replacing heavy diesel delivery vans with electric cargo tricycles for last-mile freight transportation. Six months into the initiative, municipal logs indicated that while total freight delivery volume in the district remained unchanged, total diesel van mileage within the district dropped by 45 percent. City officials concluded from these data that the initiative successfully reduced total freight-related particulate matter emissions generated within the historic district. Which of the following, if true, most seriously undermines the city officials' conclusion?

A historical study of sixteenth-century European merchant guilds revealed that guilds whose members adopted standardized accounting practices survived, on average, forty years longer than guilds that did not adopt such practices. Researchers concluded from this data that implementing standardized accounting practices directly enhanced a guild's operational resilience, enabling it to withstand severe market downturns. Which of the following best describes the flaw in the argument's reasoning?

To reduce annual municipal water expenditures during prolonged drought conditions, the city council of Northridge instituted a financial rebate for households that installed smart automated irrigation controllers. Twelve months following the implementation of the rebate program, municipal records indicated that total residential water consumption across the city had decreased by 14 percent. Consequently, the city council concluded that the smart irrigation controller rebate was directly responsible for the reduction in residential water consumption.

Consider each of the options separately and select all that identify logical vulnerabilities or flaws in the city council's reasoning.

During a five-year study of a protected forest reserve, researchers tracked the population of two owl species, the Barn Owl and the Barred Owl. The total land area of the reserve remained unchanged throughout the study, and no other owl species resided in the forest. In the first year, Barn Owls accounted for 70 percent of all owls in the reserve. By the fifth year, although the total number of owls in the reserve had doubled, the proportion of Barn Owls dropped to 40 percent. Throughout the five years, no owls died or migrated out of the reserve.

Based on the information above, which of the following statements must be true? Select all that apply.