Argument
Lifetime of sacrifice spent eating an unappealing low-fat diet is too high a price to pay for the chance of extending life for 3 months
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Modifying our diet is not worthwhile
Thoughts
There are a few assumptions that are being made here: 1) that extending life by 3 months is not worthwhile; 2) that the diet is unappealing
(A) Opposite. This would actually destroy the argument because it is basically saying that lengthening one's life IS worthwhile.
(B) Correct. This is what I expected in my #2 assumption to look for.
(C) We don't necessarily need to assume this. Suppose it is not the only relevent factor, the argument still stands perfectly fine
(D) Similar to (A), this would actually be leaning towards the opposite of what we are looking for. This answer choice is saying, "but hey! The difference in taste between 30% and 37% fat isn't really a big deal!" Also, keep in mind that the word "tastiness" may not equate to "appealing." This could be a great trick answer if phrased a different way.
(E) This doesn't get to the crux of the argument and doesn't attack the gap. The argument is talking about a lifetime of sacrifice isn't worth it for extending life by 3 months and, therefore, the diet is not worthwhile. We don't care about what everyone else is doing! We just care about this gap!