Marine biologists had hypothesized that lobsters kept together

[quote="broall"]Marine biologists had hypothesized that lobsters kept together in lobster traps eat one another in response to hunger. Periodic checking of lobster traps, however, has revealed instances of lobsters sharing traps together for weeks. Eight lobsters even shared one trap together for two months without eating one another. The marine biologists’ hypothesis, therefore, is clearly wrong.

The argument against the marine biologists’ hypothesis is based on which one of the following assumptions?

(A) Lobsters not caught in lobster traps have been observed eating one another.

(B) Two months is the longest known period during which eight or more lobsters have been trapped together.

(C) It is unusual to find as many as eight lobsters caught together in one single trap.

(D) Members of other marine species sometimes eat their own kind when no other food sources are available.

(E) Any food that the eight lobsters in the trap might have obtained was not enough to ward off hunger.


The answer is E and the explaination for the same is


And while I'm guilty of this myself many times in the past, let me try to be very precise in how the Negation Test works. It's not that the negation of the correct answer will destroy the conclusion, but that it makes it so the conclusion does not follow from the evidence offered. So after negating answer choice (E), the conclusion that lobsters do not eat one another in response to hunger may still be true, but we would not be able to use the evidence provided to support such a conclusion. An assumption of this argument is that the lobsters were in fact hungry. Without that assumption the example of the lobsters would be irrelevant to a claim about what happens to lobsters in response to hunger. Answer choice (E) simply provides this assumption.

Let's take a look at the incorrect answer choices:

(A) undermines the argument that lobsters will not each other in response to hunger.
(B) is irrelevant. Two months is more than enough time to allow a lobster to become hungry, and if it wasn't, that would again simply undermine the argument.
(C) is irrelevant. The frequency with which lobsters are caught in large groups plays no role in what happens once they are.
(D) is tempting in that it suggests the behavior is common at least on other marine species, but while it helps, it is not a Necessary Assumption of the argument.