(Sorry, if this is a repost. I searched the forum but couldn't find this question. Since this is a GMATPREP ques., there are chances that someone might have posted it as a JPG image. If so, please provide a pointer to the other thread)

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 dense tree cover that formerly was a feature of most South American coffee plantations.

Scott: The population of the spruce budworm, the warbler's favourite 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 does not eat budworms but is as dependent on South America 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 only be temporary
D. Many Tennessee warblers 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

I go with the D....

A.

In my opinion, D does weaken Scott's hypothesis somewhat by suggesting another reason for the declining number of birds; however, A is a better choice because A weakens Scott's hypothesis by directly negating his argument which suggest that the declining number of the budworm is the reason for why the number of the bird is declining.
_________________

Consider KUDOS if my post was helpful.

My Debrief: 750-q49v42-105591.html#p825487

Could someone explain why #4 does not weaken Scott's argument but #1 does? I don't get it.