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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.
原来一直觉得A选项证明力度不够，现在觉得还是有一定道理，思维如下：
题目中确定的果是，鸟少了；一个人说鸟少同时树少，所以是树少导致的鸟少；另一个人说鸟少而且虫少（吃的少），所以是虫少（吃的少）导致的鸟少；
选项A的意思是，即使吃的不少，鸟也会少；
这种论证有没有道理呢？我觉得如果类比想象一下，在一个科学实验中，A组B组都看到了一种现象，科学家试图去解释为什么会有这种现象，然后发现A组B组都有X特征，他们会更容易去想是X导致的这个现象；而A组有Y特征，B组却没有Y特征，科学家就没有很强的理由说A组的现象一定是由Y特征导致的，因为在这种情况下归因到Y显然要比归因到X要弱很多；
诚然，这种论证不能证明是A组实验中被观察到的现象一定不是Y造成的，但是却能证明A组在实验中的现象更有可能是X造成的；对于给出了两种不同的归因解释选其一的情景，确实是有weaken的效果；
回到这道题目来，如果两组鸟都减少了，一个有虫够吃一个虫不够吃，但是都面临树少，我们更有理由相信是树少导致的鸟少。虽然不能证明题目中的鸟少一定不是因为虫少造成的，但是给我们理由相信鸟少更有可能是树少造成的。
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