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, ttherefore, is clearly wrong. The argument against the marine biologists' hypothesis is based on which one of the following assumptions? ['Any food that the eight lobsters in the trap might have obtained was not enough to ward off hunger.', 'Lobsters not caught in lobster traps have been observed eating one another.', 'It is unusual to find as many as eight lobsters caught together in one single trap.', 'Two months is the longest known period during which eight or more lobsters have been trapped together.']