Question

Researchers have shown that older ants, which usually spend more time gathering nourishment for the colony, tend to have larger brains than do younger ants, which usually help nurture ant larvae in the colony. Since gathering nourishment requires greater cognitive skills than does nurturing larvae, it would appear that such gathering leads to the increased brain size of older ants.
Which of the following, if true, most seriously weakens the argument above?

A. Ants that have spent more time gathering nourishment do not have considerably larger brains than do ants that have spent a much shorter time gathering.
B. The brains of older ants that stop gathering nourishment to take on other tasks do not become smaller.
C. The brains of older ants that are not involved in gathering nourishment are the same size as those counterparts of the same age that do gather nourishment.
D. In many species of ants, the brains of older ants are only minimally larger than the brains of younger ants.
E. Ants that have to travel farther to gather nourishment do not have considerably larger brains than do ants that do not have to travel far.

Answer 1

The correct answer is C) The brains of older ants that are not involved in gathering nourishment are the same size as those counterparts of the same age that do gather nourishment.

The statement that most seriously weakens the argument above is "The brains of older ants that are not involved in gathering nourishment are the same size as those counterparts of the same age that do gather nourishment."

Researchers have shown that older ants, which usually spend more time gathering nourishment for the colony, tend to have larger brains than do younger ants, which usually help nurture ant larvae in the colony. Since gathering nourishment requires greater cognitive skills than does nurture larvae, it would appear that such gathering leads to the increased brain size of older ants. But the brains of older ants that do not collect food have the same size of the brain. So there is not a direct correlation between the age of the ants and the brain size, regarding the activity they do.

Answer 2

The right answer is:  

C. The brains of older ants that are not involved in gathering nourishment are the same size as those counterparts of the same age that do gather nourishment.  

Explanation

If this statement were true it would seriously weaken the original argument because we would actually be taking into consideration age as well as activity of the ants.