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题库 / Prep2008E2-CR-92
Kate: The recent decline in numbers of the Tennessee warbler, a North American songbird that migrates each fall to coffee plantations in South America, is due to the elimination of the dense tree cover that formerly was a feature of most South American coffee plantations.
Scott: The population of the spruce budworm, the warbler's favorite prey in North America, has been dropping. This is a more likely explanation of the warbler's decline.
Which of the following, if true, most seriously calls Scott's hypothesis into question?
The numbers of the Baltimore oriole, a songbird that does not eat budworms but is as dependent on South American coffee plantations as is the Tennessee warbler, are declining.
The spruce budworm population has dropped because of a disease that can infect budworms but not Tennessee warblers.
The drop in the population of the spruce budworm is expected to be only temporary.
Many Tennessee warblers have begun migrating in the fall to places other than traditional coffee plantations.
Although many North American songbirds have declined in numbers, no other species has experienced as great a decline as has the Tennessee warbler.
前提： The recent decline in numbers of the Tennessee warbler（结果） 结论：due to the elimination of the dense tree cover that formerly was a feature of most South American coffee plantations.这种鸟会在秋天迁徙到南美一个种了咖啡作物的地方，所以鸟的数量减少的原因是因为那个地方的咖啡作物减少了（k）。（s）认为是因为这个鸟的一种食物——spruce budworm的数量少了，才导致这种鸟的数量减少的。要求削弱s的看法。也就是提出并不是因为spruce budworm减少而导致鸟的数量减少，而是他因。a的选项是给出了一个与 Tennessee warbler鸟相似的类比，这种鸟也是喜欢咖啡作物，但是它的食物不是这种虫子，它的数量也和这种鸟一样减少了。所以是相同类比，将s的观点削弱了。
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