GWD TN 2-38 或 GWD3-Q38

GWD3-Q38:

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?

A.    The numbers of the Baltimore oriole, a songbird that dose not eat budworms but is as dependent on South American coffee plantations as is the Tennessee warbler, are declining.

B.    The spruce-budworm population has dropped because of a disease that can infect budworms but not Tennessee warblers.

C.    The drop in the population of the spruce budworm is expected to be only temporary.

D.    Many Tennessee warbler have begun migrating in the fall to places other than traditional coffee plantations.

E.     Although many North American songbirds have declined in numbers, no other species has experienced as great a decline as has the Tennessee warbler.

A项，Baltimore oriole数量减少也可能因为其它原因，如人类捕杀等，不能说明Scott是错的。

D项为什么是无关呢？

D项，many Tennessee warbler迁徙到非traditional coffee plantation的地方，是致使Tennessee warbler迁徙到South American coffee plantations的数量下降的原因，因此削弱了Scott的假设。

仔细想想虽然D项可能也不够说服力，但我认为比起A来好一点。

盼帮助，谢谢～