All practice questions

A municipality installed bright LED street lighting along main thoroughfares last year. Over the same period, night-time traffic accidents on those thoroughfares decreased by 15 percent. The mayor concluded that the improved visibility from the new street lights directly caused the reduction in night-time traffic accidents. Which of the following, if true, most seriously weakens the mayor's argument?

A financial advisory firm manages two types of investment accounts: Growth portfolios and Conservative portfolios. Each Growth portfolio generates $\$5,000$ in annual dividends and $\$12,000$ in annual capital gains. Each Conservative portfolio generates $\$8,000$ in annual dividends and $\$4,000$ in annual capital gains. Last year, the firm generated a total of $\$186,000$ in dividends and $\$188,000$ in capital gains from these portfolios. What was the total number of portfolios (Growth and Conservative combined) managed by the firm?

Read the passage below and match each cited excerpt or claim to its exact structural function within the passage.

In recent evolutionary anthropology, scholars have debated whether the acquisition of fire by early hominins primarily served nutritional purposes through cooking or social purposes through communal gathering. Proponents of the cooking hypothesis argue that thermal processing of food dramatically increased caloric availability, enabling rapid encephalization. To substantiate this claim, researchers frequently cite archaeological findings of burned animal bones and heat-altered stone tools dated to approximately 1.8 million years ago.

However, a growing contingent of evolutionary theorists contends that reducing the role of fire to metabolic optimization underestimates its cognitive impact. They assert that the nocturnal prolongation of social activity facilitated by firelight fostered complex narrative structures, vocal storytelling, and social bonding mechanisms. Empirical evidence supporting this perspective stems from comparative analyses of contemporary hunter-gatherer campfire conversations, which focus heavily on myth-making and social governance rather than daytime transactional topics. Ultimately, while dietary energy remains a critical physical prerequisite, the primary transformative evolutionary force of controlled fire lay in its restructuring of hominin social consciousness.

Match each passage excerpt (left) with its corresponding structural function (right):

At the beginning of 2021, a technology startup had an initial valuation of $V$ dollars. Over the next three years, its valuation experienced the following successive annual percentage changes:
- In 2021, the valuation increased by $20\%$.
- In 2022, the valuation decreased by $10\%$ relative to its valuation at the end of 2021.
- In 2023, the valuation increased by $50\%$ relative to its valuation at the end of 2022.

If the startup's valuation at the end of 2023 was $\$648,000$, what was its initial valuation $V$ at the beginning of 2021?

In deep-sea hydrothermal vent ecosystems, the presence of chemoautotrophic bacteria supporting complex metazoan communities has long presented an evolutionary puzzle regarding the origin of endosymbiosis. Traditional models posited that ancestral host invertebrates actively engulfed free-living sulfur-oxidizing bacteria through phagocytosis, subsequently establishing stable metabolic cooperativity. This horizontal acquisition hypothesis accounted for the genetic divergence observed between host nuclear genomes and bacterial symbiont lineages across isolated vent fields. However, recent phylogenomic analyses of the vestimentiferan tubeworm Riftia pachyptila and its obligate endosymbiont Candidatus Endoriftia persephone reveal an unexpected pattern of genomic decay in the symbiont's regulatory pathways, coupled with high levels of host-mediated gene expression control. These findings challenge the assumption of autonomous bacterial adaptation prior to integration. Instead, the evidence suggests a model of co-evolutionary entrapment, wherein the host organism progressively exploited pre-existing metabolic leakages of ambient bacteria, forcing metabolic reliance before functional integration was complete. While some researchers contend that this host-driven model overstates host agency by underestimating the role of mobile genetic elements in bacterial pre-adaptation, their critique fails to explain why free-living bacterial populations maintain intact regulatory cascades absent in vent-bound lineages. Thus, rather than viewing endosymbiosis in vent fauna as the result of mutualistic convergence or passive bacterial colonization, scholars must recognize it as a specialized form of metabolic subjugation shaped primarily by host genomic dominance over evolutionary time.

Which of the following best states the primary purpose of the passage?

Although evolutionary biologists long held that genetic mutations driving adaptive traits arise entirely at random prior to environmental exposure, recent studies of epigenetically inherited stress responses in marine invertebrates suggest that environmental stressors can systematically alter chromatin structure in parental germ cells, thereby pre-adapting subsequent generations to specific ecological pressures without modifying the underlying DNA sequence.

Which of the following is most strongly supported by the statement above regarding the recent studies of marine invertebrates?

If $x > 1$ is an integer such that $\sqrt{x + 2\sqrt{x - 1}} + \sqrt{x - 2\sqrt{x - 1}} = 6$, what is the value of $x$?

Read the following passage excerpt regarding early agricultural economic history:

'Although late nineteenth-century agrarian cooperatives in the American Midwest frequently declared complete financial independence from commercial lending houses, their surviving operational ledgers reveal that nearly all of these organizations relied regularly on short-term bank credit to purchase seasonal harvests from local farmers.'

Which of the following statements about late nineteenth-century agrarian cooperatives in the American Midwest is most strongly supported by the passage excerpt?

For decades, marine biogeochemists operated under the assumption that primary production at deep-sea hydrothermal vents was almost exclusively driven by obligate chemolithoautotrophic bacteria, which generate organic compounds by oxidizing reduced sulfur or iron compounds. Early oceanographic surveys reinforced this paradigm by demonstrating that vent microbial mats were dominated by taxa possessing metabolic pathways strictly dedicated to inorganic carbon fixation. Consequently, classic models of abyssal food webs framed these chemoautotrophic microbes as the sole primary energetic foundation supporting specialized benthic megafauna in light-deprived oceanic basins.

However, recent genomic sequencing of uncultivated vent archaea has revealed a far more complex metabolic landscape than previously recognized. Rather than relying solely on inorganic chemical energy, several newly identified lineages express genes for facultative mixotrophy—the capability to assimilate dissolved organic carbon alongside inorganic carbon fixation depending on local geochemical gradients. While some researchers initially dismissed mixotrophic pathways as minor evolutionary adaptations restricted to peripheral microhabitats, subsequent transcriptomic profiling confirmed that mixotrophic metabolic activity surges dramatically during periods of fluctuating fluid flow.

Nonetheless, this metabolic flexibility does not imply that obligate chemoautotrophy is ecologically secondary. On the contrary, quantitative isotopic tracer analyses indicate that obligate autotrophs maintain the baseline primary productivity required to sustain high-density vent communities during steady-state conditions. Ultimately, the discovery of mixotrophy does not overturn the fundamental role of inorganic carbon fixation; rather, it refines structural models of vent ecosystems by explaining how microbial communities maintain metabolic resilience during environmental perturbations.

Which of the following best describes the overall logical trajectory and structural organization of the passage?

For decades, ornithologists believed that migratory birds navigated across long distances primarily by sensing the orientation of the Earth's magnetic field through iron-oxide crystals located in their beaks. This classical mechanical hypothesis provided an intuitive framework that dominated avian biology literature and guided field research for over thirty years.

However, recent laboratory findings have significantly weakened this traditional consensus. High-resolution imaging and behavioral trials revealed that disrupting the neural pathways connected to beak iron deposits did not impair orientation abilities in migratory robins. Instead, optical experiments revealed that birds rely on light-dependent radical pair reactions in specialized cryptochrome proteins in their eyes, effectively allowing them to visualise magnetic lines.

Building upon these findings, contemporary biophysicists have formulated an integrated dual-mechanism framework. This updated paradigm posits that while ocular cryptochromes provide the primary compass for directional orientation, beak receptors function secondarily as a magnetic map for positional intensity.

Which of the following best describes the overall logical structure of the passage?

Passage:
In evolutionary ecology, floral scent polymorphism—the phenomenon in which individuals of a single plant species emit markedly different volatile organic chemical profiles—was historically regarded as an selectively neutral trait maintained principally through stochastic genetic drift. However, recent empirical investigations into alpine angiosperm populations have challenged this traditional view, positing instead that scent variation is dynamically sustained by opposing selective pressures exerted by mutualist pollinators and antagonist florivores.

Proponents of this adaptive framework observe that while elevated emissions of volatile monoterpenes enhance reproductive fitness by significantly increasing visitation rates from high-efficiency bumblebee pollinators, these same chemical signals inadvertently cue specialist beetle herbivores to plant locations, resulting in severe floral damage and reduced seed viability. Conversely, chemotypes characterized by suppressed volatile profiles experience diminished pollination frequency yet achieve higher overall survival by escaping heavy herbivory. Mathur and Varga investigated this ecological trade-off by quantifying lifetime fitness across microhabitats characterized by varying antagonist densities. Their findings reveal that spatial variation in herbivore pressure establishes a dynamic mosaic of balancing selection: high-emission phenotypes maintain a selective advantage in low-density alpine meadows, whereas low-emission phenotypes predominate in herbivore-dense subalpine zones. Consequently, scent polymorphism is best understood not as a byproduct of random evolutionary processes, but as a balanced adaptation maintained by spatially heterogeneous selection pressures.

Statement: The primary purpose of the passage is to present evidence refuting the traditional neutralist view of floral scent polymorphism in favor of an adaptive model driven by spatially variable selective pressures.

Passage:
For decades, plant physiologists regarded the emission of volatile organic compounds (VOCs) by damaged plants primarily as metabolic byproducts of cellular stress or as direct deterrents against herbivores. However, controlled experiments in the late 1990s revealed that neighboring, undamaged plants exposed to these airborne signals upregulate their own chemical defenses prior to attack. This discovery prompted some researchers to contend that plants actively engage in intentional inter-plant communication.

Yet, this communicative hypothesis drew scrutiny from evolutionary biologists, who argued that natural selection rarely favors altruistic signaling between non-kin individuals when such signals incur metabolic costs without conferring direct fitness benefits to the emitter. Instead, critics proposed an alternative framework: VOC emissions originally evolved as a vascularly constrained self-signaling mechanism. Because internal systemic transport within a single plant can be slow or structurally obstructed, airborne signaling allows distant leaves of the same organism to coordinate defensive responses rapidly. Eavesdropping by neighboring plants is thus best understood as an incidental ecological byproduct rather than an evolutionary adaptation driven by altruism. Recently, integrated ecological models have begun to synthesize these perspectives by examining microclimate variations and genetic relatedness within plant clusters, shifting consensus toward viewing VOC phenomena through the dual lenses of kin selection and self-signaling efficiency.

Which of the following best states the primary purpose of the passage?

For decades, oceanographic consensus maintained that biological productivity in High-Nutrient, Low-Chlorophyll (HNLC) ocean regions was constrained almost exclusively by physical variables—such as solar irradiance and seasonal mixed-layer dynamics—alongside macro-nutrient concentrations of nitrate and phosphate. Standard biogeochemical models presupposed that essential trace elements were supplied in abundance through deep-water upwelling, thereby framing phytoplankton growth as a predictable function of seasonal light exposure rather than chemical micro-nutrient limitation.

This paradigm was fundamentally disrupted when oceanographer John Martin advanced the Iron Hypothesis, contending that dissolved iron—a trace micro-nutrient primarily delivered via atmospheric aeolian dust—serves as the primary catalyst for photosynthetic production in HNLC zones. Initial mesoscale iron-enrichment experiments corroborated Martin’s thesis, demonstrating that artificially infusing surface waters with ferrous iron induced immediate, massive diatom blooms. Nevertheless, contemporary marine ecologists urge caution, revealing that while short-term iron additions stimulate rapid surface productivity, they simultaneously accelerate the depletion of ambient silicic acid, ultimately triggering shifts toward smaller, non-diatom assemblages that sequester significantly less organic carbon into the mesopelagic zone than initially predicted.

Far from invalidating the core premise of iron limitation, these unintended ecological consequences illustrate the inadequacy of evaluating micro-nutrient dynamics through a single-variable framework. By demonstrating how trace element surges destabilize secondary nutrient cycles, recent findings function not to discredit Martin’s foundational insight, but rather to establish that long-term carbon sequestration efficacy depends upon complex ecological succession rather than ephemeral photosynthetic spikes.

Which of the following best describes the structural role played by the second paragraph in the overall development of the passage?

For decades, researchers studying deep-sea hydrothermal vent ecosystems assumed that primary productivity relied exclusively on chemosynthetic bacteria utilizing hydrogen sulfide. However, a 2018 expedition to the Mid-Atlantic Ridge led by Dr. Elena Vance revealed an unanticipated metabolic pathway. Vance and her team isolated a novel strain of gammaproteobacteria, designated strain Alpha-7, that derives energy primarily from the oxidation of dissolved iron rather than sulfur compounds.

Unlike sulfur-oxidizing microbes, which deposit elemental sulfur externally as a metabolic byproduct, strain Alpha-7 precipitates insoluble iron oxides internally within specialized intracellular vesicles. Laboratory assays demonstrated that this internal sequestration protects the bacterium from iron toxicity while simultaneously generating a localized proton gradient across the inner membrane. This gradient drives ATP synthesis even in low-oxygen microenvironments surrounding fluid discharge vents. Furthermore, Vance observed that while sulfur-oxidizing strains thrive predominantly in high-temperature zones exceeding 60°C, strain Alpha-7 achieves peak metabolic rates in cooler, ambient waters between 15°C and 25°C. This temperature preference enables Alpha-7 to colonize peripheral regions of vent fields previously deemed biological deserts.

Based on the passage, which of the following is explicitly stated regarding the metabolic byproducts of strain Alpha-7?

An event organizer is scheduling a conference featuring $7$ distinct speakers: $3$ technology experts, $3$ finance experts, and $1$ keynote presenter. The $7$ speakers will give back-to-back presentations on a single main stage. If all $3$ technology experts must speak consecutively in any order, and no two finance experts may speak consecutively, how many different presentation schedules are possible?

If $m$ and $n$ are real numbers such that $m < 0 < n$ and $m^2 - 3mn - 4n^2 = 0$, what is the value of $\frac{m + 2n}{m - n}$?

For several decades, paleoclimatologists posited that the abrupt cooling event during the Younger Dryas period was triggered solely by a catastrophic outburst of glacial meltwater from Lake Agassiz into the North Atlantic, which severely disrupted the Atlantic Meridional Overturning Circulation (AMOC). Proponents of this single-cause hypothesis cited marine sediment cores showing sudden drops in surface ocean temperatures alongside isotopic shifts indicating a massive influx of freshwater. However, this traditional framework fails to account for recent high-resolution ice core data from Greenland, which reveal that atmospheric circulation shifts preceded the thermohaline slowdown by several decades, suggesting that oceanic disruption was a secondary consequence rather than the primary driver of the cooling anomaly.

To reconcile these temporal discrepancies, a revised atmospheric-oceanic model proposes that planetary wave perturbations, prompted by changes in Laurentide ice sheet topography, initially altered northern jet stream paths. This atmospheric reorganization redistributed thermal energy globally well before meltwater pulses destabilized ocean currents. While freshwater input undoubtedly amplified and prolonged the freezing conditions, treating ocean circulation collapse as the initial trigger conflates a reinforcing feedback mechanism with the primary catalyst. Ultimately, evaluating paleoclimate transitions requires recognizing that while localized oceanic data provide essential supporting evidence of climate amplification, the overarching driver of the shift lay in large-scale atmospheric dynamics.

Which of the following best states the main thesis of the passage as distinguished from its supporting evidence?

Consider the following sentence from an academic text on historical linguistics:

"Although nineteenth-century comparative linguists initially posited that Proto-Indo-European possessed a fully developed three-gender noun system, subsequent structural analysis of Anatolian tablets revealed that the archaic Anatolian branch preserved an earlier stage of the language featuring only an animate-inanimate distinction."

True or False: Based on the sentence above, it can be inferred that nineteenth-century comparative linguists formulated their initial hypothesis about Proto-Indo-European noun gender without incorporating structural evidence from Anatolian tablets.

A commercial bakery produces two batches of bread dough. Batch X consists of $30$ kilograms of dough with a sugar concentration of $12\%$ by weight. Batch Y consists of $45$ kilograms of dough with a sugar concentration of $20\%$ by weight. If Batch X and Batch Y are mixed together completely, what is the sugar concentration, as a percentage by weight, of the combined mixture?

Read the following passage carefully:

For decades, paleoclimatologists attributed the mid-Holocene thermal maximum primarily to orbital forcing, asserting that peak insolation directly governed global surface temperature shifts. Under this prevailing view, early climate simulations presumed a synchronous, planet-wide thermal response to astronomical cycles.

However, recent multi-proxy reconstructions from high-latitude marine sediments revealed pronounced thermal asymmetries that orbital models failed to predict. To account for these discrepancies, dynamic vegetation feedback theories emerged, contending that land-surface albedo changes amplified localized warming independently of direct solar radiation.

Most recently, synthesis studies have demonstrated that these proxy anomalies stem from seasonal recording biases inherent to marine planktonic organisms rather than true mean-annual temperature shifts. By accounting for this proxy seasonality, researchers reconciled the divergent models, establishing that orbital forcing dictates the foundational climate trajectory while vegetation dynamics act strictly as a secondary, seasonally constrained modifier.

Below are three descriptions of the structural functions performed by the paragraphs in the passage. Arrange the descriptions in the correct sequential order matching Paragraph 1, Paragraph 2, and Paragraph 3.