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Which of the following most accurately describes the organization of the passage?
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It can be inferred that both Burckhardt and Kelly have been criticized by the scholars mentioned in highlight text for which of the following?
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The last sentence in the passage serves primarily to
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Most attempts by physicists to send particles faster than the speed of light involve a remarkable phenomenon called quantum tunneling, in which particles travel through solid barriers that appear to be impenetrable. If you throw a ball at a wall, you expect it to bounce back, not to pass straight through it. Yet subatomic particles perform the equivalent feat. Quantum theory says that there is a distinct, albeit small, probability that such a particle will tunnel its way through a barrier; the probability declines exponentially as the thickness of the barrier increases. Though the extreme rapidity of quantum tunneling was noted as early as 1932, not until 1955 was it hypothesized－by Wigner and Eisenbud－that tunneling particles sometimes travel faster than light. Their grounds were calculations that suggested that the time it takes a particle to tunnel through a barrier increases with the thickness of the barrier until tunneling time reaches a maximum; beyond that maximum, tunneling time stays the same regardless of barrier thickness. This would imply that once maximum tunneling time is reached, tunneling speed will increase without limit as barrier thickness increases. Several recent experiments have supported this hypothesis that tunneling particles sometimes reach superluminal speed. According to measurements performed by Raymond Chiao and colleagues, for example, photons can pass through an optical filter at 1.7 times the speed of light.
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The passage implies that if tunneling time reached no maximum in increasing with barrier thickness, then
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Which of the following statements about the earliest scientific investigators of quantum tunneling can be inferred from the passage?
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The primary purpose of the passage is to
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It can be inferred from the passage that the research mentioned in highlight text supports which of the following statements?
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Suppose we were in a spaceship in free fall, where objects are weightless, and wanted to know a small solid object's mass. We could not simply balance that object against another of known weight, as we would on Earth. The unknown mass could be determined, however, by placing the object on a spring scale and swinging the scale in a circle at the end of a string. The scale would measure the tension in the [hl:2]string[/hl:2], which would depend on both the speed of revolution and the mass of the object. The tension would be greater, the greater the mass or the greater the speed of revolution. From the measured tension and speed of whirling, we could determine the object's mass.Astronomers use an analogous procedure to “weigh” double-star systems. The speed with which the two stars in a double-star system circle one another depends on the gravitational force between them, which holds the system together. This attractive force, analogous to the tension in the string, is proportional to the stars' combined mass, according to Newton's law of gravitation. By observing the time required for the stars to circle each other (the period) and measuring the distance between them, we can deduce the restraining force, and hence the masses.
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The author of the passage mentions observations regarding the period of a double-star system as being useful for determining
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The primary purpose of the passage is to
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The passage suggests which of the following about the micro-wear patterns found on the teeth of omnivorous primates?
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It can be inferred from the passage that Walker's conclusion about the australopithecine diet would be called into question under which of the following circumstances?
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Travelers to Mars would have to endure low levels of gravity for long periods of time, avoid large doses of radiation, contend with the chemically reactive Martian soil, and perhaps even having to ward off contamination by Martian life-forms.
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Schistosomiasis, a disease caused by a parasitic worm, is prevalent in hot, humid climates, and it has become more widespread as irrigation projects have enlarged the habitat of the freshwater snails that are the parasite's hosts for part of its life cycle.
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In the 1980s the federal government was the largest single provider of day care for children, offering child care, health, and educational services to hundreds of thousands of children from poor households through the Head Start program and which supported private day-care facilities through childcare tax credits, state block grants, and tax breaks for employers who subsidized day-care services.
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Astronomer: Most stars are born in groups of thousands, each star in a group forming from the same parent cloud of gas. Each cloud has a unique, homogeneous chemical composition. Therefore, whenever two stars have the same chemical composition as each other, they must have originated from the same cloud of gas.Which of the following, if true, would most strengthen the astronomer's argument?
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A newly discovered painting seems to be the work of one of two seventeenthcentury artists, either the northern German Johannes Drechen or the Frenchman Louis Birelle, who sometimes painted in the same style as Drechen. Analysis of the carved picture frame, which has been identified as the painting's original seventeenth-century frame, showed that it is made of wood found widely in northern Germany at the time, but rare in the part of France where Birelle lived. This shows that the painting is most likely the work of Drechen.Which of the following is an assumption that the argument requires?
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Economist: The most economically efficient way to reduce emissions of air pollutants is to tax them in proportion to the damage they are likely to cause. But in Country Y, many serious pollutants are untaxed and unregulated, and policy makers strongly oppose new taxes. Therefore, the best way to achieve a reduction in air pollutant emissions in Country Y would be to institute fixed upper limits on them.Which of the following is an assumption of the economist's argument?
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Coffee shop owner: A large number of customers will pay at least the fair market value for a cup of coffee, even if there is no formal charge. Some will pay more than this out of appreciation of the trust that is placed in them. And our total number of customers is likely to increase. We could therefore improve our net cash flow by implementing an honor system in which customers pay what they wish for coffee by depositing money in a can.Manager: We're likely to lose money on this plan. Many customers would cheat the system, paying a very small sum or nothing at all.which of the following, if true, would best support the owner's plan, in light of the manager's concern?
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