Derek won this year's school science fair and is a star on both the school's football and basketball teams. Outside of school, he runs his own successful business and is an accomplished musician. Obviously, Derek is good at everything he does. Therefore, he will undoubtedly make an excellent Student Government President if elected.
The argument above is suspect, because it overlooks the possibility that
A. Derek participates only in those activities at which he knows he will excel.
(A) is correct. This was a difficult question; it's important to pay attention to precisely what the argument is claiming, which in this case is that Derek will make an excellent S.G. President because he is "good at everything he does." The stimulus names five specific things that Derek is "good at" (science, football, basketball, business, music) to support the claim that he is "good at everything he does." But if it is true that Derek only participates in those activities at which he knows he will excel, then he might not be "good at" anything other than the five activities specified. Therefore (A) is the best answer.
B. being Student Government President requires different skills than those needed to become an accomplished musician.
(B) is incorrect because it draws a distinction with only one of the five specified activities that Derek is "good at." If the choice had named and distinguished all five, instead of just this one, it would have been a better answer, and would have essentially implied the same thing that (A) implies, i.e., being "good at" one thing does not necessarily make someone "good at" another. But by itself, the distinction between leadership ability and musical talent is insignificant, especially when success at academics, sports and business are much better indicators of leadership potential.
C. school, sports, music and business are the only activities in which Derek is engaged.
(C) is incorrect because this possibility does not undermine the argument. (C) is different from (A) because if these are the only activities that Derek does, that nevertheless does not preclude the possibility that he might make a very good S.G. President, based on the claim that he is "good at" all of the named activities. (A) adds the element of intent, i.e., Derek only does these activities because he knows he is "good at" them, which opens up the possibility, if not the likelihood, that he would not be "good at" anything else.
D. there may be other students who are just as qualified as Derek to be Student Government President.
(D) is incorrect because it also does not undermine the argument. The fact that others may be just as qualified does not diminish Derek's qualifications. The argument makes no attempt to compare Derek to anyone else; it only claims that Derek would make an excellent S.G. President, not that he is the best choice among those available. (D) is a non-sequitur; put simply, it doesn't matter.
E. Derek has no time in his schedule to devote to Student Government.
(E) is incorrect because, like (D), it raises a separate and unrelated issue; another non-sequitur. The argument is claiming that he would make an excellent President, which is still a valid argument whether or not he would actually be willing or able to put in the time required to serve the office if he is elected.