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Which of the following, if true, would enable the conclusion of the argument to be properly drawn?
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Recently an unusually high number of dolphins have been found dead of infectious diseases, and most of these had abnormally high tissue concentrations of certain compounds that, even in low concentrations, reduce dolphins` resistance to infection. The only source of these compounds in the dolphins` environment is boat paint. Therefore, since dolphins rid their bodies of the compounds rapidly once exposure ceases, their mortality rate should decline rapidly if such boat paints are banned.
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Which of the following, if true, most strengthens the argument?
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Iridium, a hard, whitish metal similar to platinum, is extremely rare on Earth. Extremely high concentrations of iridium on Earth result from only two scenarios: massive volcanic eruptions that release iridium from deep within the Earth and meteorites that shower down on Earth from space. When scientists found concentrations of iridium 30 times higher than normal in rock stratum from 65 million years ago, they concluded that a massive meteor or comet hit the Earth and caused the massive extinction of the dinosaurs.
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Which of the following, if true, most strongly supports the scientist`s conclusion?
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Upon maturity, monarch butterflies travel hundreds of miles from their places of origin and lay their eggs on milkweed. The caterpillars that emerge feed on milkweed and absorb the glycosides in milkweed sap. The specific glycosides present in milkweed differ from region to region within the monarch butterfly`s range. Since mature butterflies retain the glycosides, the glycosides in a mature monarch butterfly could be used to determine its place of origin.
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Which of the following, if true, most strengthens the argument?
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Monarch butterflies lay their eggs hundreds of miles away from their places of origin. Each caterpillar that emerges feeds exclusively on milkweed, absorbing the glycosides that milkweed contains. Butterflies retain the glycosides they absorb as caterpillars. Research on monarch butterflies whose migration has been tracked shows that the combination of glycosides in a butterfly always exactly matches the distinctive combination of glycosides that exists in the species of milkweed in the butterfly's place of origin.
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If the information provided is true, which of the following is most strongly supported on the basis of it?
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When rats are placed under conditions of stress, their adrenal glands immediately increase production of the hormone corticosterone, and soon thereafter the rats` white blood cell count drops substantially. Yet rats without functioning adrenal glands experience little decrease in white blood cell count when placed under conditions of stress. It is likely, therefore, that an increase in corticosterone produced by a rat`s adrenal glands causes the rat`s white blood cell count to decrease.
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Which of the following would it be most useful to know in evaluating the reasoning of the argument?
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Some psychologists have proposed the hypothesis that children in different cultures have different psychologies, demonstrated, for example, by culture-specific tendencies for the children`s behavior to be relatively self-assertive or obedient. However, that hypothesis is incorrect, since the psychological mechanisms by which children acquire behavioral traits are identical for all cultures.
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In the argument, the author`s position and the position challenged by the author differ in the criteria they use to distinguish different
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Scholars have tended to treat the ideas of American social reformer Jane Addams as unique, failing to compare them sufficiently those of other social activists and public intellectuals. Recent work, however, has situated her more thoroughly in the thinking and events of her time. For example, labor historians have usefully contextualized Addams` close work with labor unions in the 1890s. When Addams` interest in the workers` reform agenda is understood in relation to the history of trade unionism in Chicago and its impressive record of political action, her contribution emerges as far more cooperative than groundbreaking. Workers influenced her in ways not preciously appreciated. Such contextualizing efforts make it possible to see what Addams learned from other reformers and what she contributed herself.
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The primary purpose of the passage is to
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The author refers to the "history of trade unionism in Chicago"primarily as
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Because different mammalian species favor different environments, identifying and counting bones from prehistoric deposits in caves can reveal much about climatic change. However, using large mammals` bones can be problematic. Some species, such as red deer, are very adaptable -- both on open grassland and in thick woodland. Moreover, some large-animal bones may have traveled considerable distances before being discarded: both carnivores and humans can have large hunting territories and bring home large animals quite unlike those near their den or campsite. Consequently, the bones of the small mammals found with cave sediments provide a better index of climate change they are generally more numerous, the species are more sensitive to environmental conditions, and few travel far within their short lives.
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The passage mentions which of the following as an obstacle to using animal bones to reconstruct past climate changes?
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The passage mentions "red deer" as an instance of an animal that
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Seeding a forest with nonnative species after a fire can impede native plant regeneration and spread invasive species in vulnerable fire-affected soils. Moreover, native seed sources are almost always sufficient for early nature reestablishment of native species, so planting should be considered only when natural regeneration is unlikely. Replanting dense stands of fast-growing conifers---a common postfire management practice---truncates the biologically rich early stage of ecological succession and can increase the severity of future fires. Other treatments should be carefully scrutinized for their potential to spread noxious weeds. For instance, straw mulch applied extensively to reduce erosion after the 2002 Hayman Fire in Colorado was contaminated with cheatgrass, an invasive grass difficult to control or eradicate once established.
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