You bet, supernerd! The question is asking us to look to these lines:
From his studies he concluded that many earlier classifications of the relationships of bird families were wrong. For instance, he said that vultures found in North and South America were more closely related to storks than to European vultures, and that loons and grebes, which many taxonomists had argued were closely related, were not.
We are supposed to see what those lines "challenge," and so this is a type of Cannot Be True question. If Sibley is correct in these lines, then which of the answers cannot be true?
Answer C is correct because it directly conflicts with what Sibley said. Vultures in North and South America are more like storks than like European vultures, so they are not likely to be the same species as those European vultures!
The other answers are all incorrect for a variety of reasons that mostly boil down to "that's not what Sibley is saying" and "we don't really have any information about that." For example, answer E: I have no idea what Sibley would say or what his evidence would show about vultures in North and South America as compared to
each other. I only know what he would say about the two groups
together compared to vultures in Europe and also to storks.
Adam M. Tyson
PowerScore LSAT, GRE, ACT and SAT Instructor
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