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A major chemical spill occurred five years ago at Baker’s Beach, the world’s sole nesting ground for Merrick sea turtles, and prevented nearly all the eggs laid that year from hatching. Yet the number of adult female Merricks returning to lay their eggs at Baker’s Beach has actually increased somewhat since five years ago. Clearly, environmentalists’ prediction that the world’s Merrick population would decline as a result of the spill has proven unfounded. Which of the following, if true, most seriously undermines the argument offered in refutation of the environmentalists’ prediction?
A. The chemical spill five years ago occurred at a time when there were neither Merrick sea turtles nor Merrick sea turtle eggs on Baker’s Beach. B. Female Merrick sea turtles begin returning to Baker’s Beach to lay their eggs when they are ten years old. C. Under normal conditions, only a small proportion of hatchling female Merrick sea turtles survive in the ocean until adulthood and return to lay their eggs at Baker’s Beach. D. Environmental pressures unrelated to the chemical spill have caused a significant decline in the population of one of the several species of sea birds that prey on Merrick sea turtle eggs. E. After the chemical spill, an environmental group rejected a proposal to increase the Merrick sea turtle population by transferring eggs from Baker’s Beach to nearby beaches that had not been affected by the spill. 答案 B ， 但无法排除D, D说捕食海龟的鸟少了。说明龟的增加不能说明是污染没有作用，污染其实是有害的，但捕食者少了，导致海龟数量增加掩盖了污染的副作用。所以D是削弱。 请牛牛解惑！ | 
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发表于 2009-2-19 12:40:00
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