GWD-3-38

答案是A.  其实就是举了一个反例，这个我懂。

我想问：D为什么不正确？谢谢！

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?

1. 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.
   
2. The spruce-budworm population has dropped because of a disease that can infect budworms but not Tennessee warblers.
   
3. The drop in the population of the spruce budworm is expected to be only temporary.
   
4. Many Tennessee warbler have begun migrating in the fall to places other than traditional coffee plantations.
   
5. Although many North American songbirds have declined in numbers, no other species has experienced as great a decline as has the Tennessee warbler.

置顶贴里面有详细讨论，请查清后再发问，谢谢。

http://forum.chasedream.com/dispbbs.asp?BoardID=24&ID=64928

做这种削弱题，一定要注意问的是什么，结论是什么。

Scott的结论是：This（The population of the spruce budworm dropping） is a more likely explanation of the warbler’s decline.

问的是能最大限度削弱Scott的结论。

D说这种鸟开始往别的地方迁徙了；其实，D是很间接的一个选项；飞往别的地方并不能直接排除猎物少了的解释；而A可以直接反驳Scott的观点。

谢谢老大！！

但是不能用她因来解释D选项的削弱作用吗？

我想了又想，觉得主要是因为D选项中的have been 在作怪。如果说；飞往别的地方 have been occured for some time, then why the decline of the numbers of the Tennessee warbler occured only recently?  Thus, what meantioned in D cannot afford a good reason for the recent decline.

是不是这样子啊。。。老大？请多多指教！

个人觉得这也是他因，但是没有排除Scott的观点的可能；比如，是不是因为猎物减少了才开始迁徙的，这样的话就不好解释了。

这个也不好解释，原文Scott的时态也是完成时的进行时has been dropping；跟时态关系不大。

个人意见。

谢谢ethyl. 我回头再仔细看了看选项。发现了这个东西，可能我两都忽视了

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

但是原文根本就没有对coffee plantation进行区分。所以无法削弱。

对吗？

这个……

traditional应该就是指原来的coffee plantations吧

那。。。

老大的意思是说，

那这题选的是最优答案，而非正确答案了？-- D没有错，只是不如A好？

呵呵，对啊。

GMAT逻辑、语法甚至阅读有不少答案是要挑最好的、最适合的；逻辑题更是如此啦，要不然为什么问题问的时候说most什么什么的……