Adult female rats who have never before encountered rat pups

We need something that explains why the amount of time it takes for adult female rats to start showing maternal behaviors "can be considerably shortened by disabling the female's sense of smell or by removing the scent-producing glands of the pup." So we need to compare adult females who CAN pick up the scent of the pups to adult females who CANNOT pick up the scent of the pups.


We are not trying to explain a difference between female rats who have given birth and female rats who have never given birth. Instead, we are trying to compare adult females who CAN pick up on the scent of the pups to adult females who CANNOT pickup on the scent of the pups. Choice (D) does not explain why the group who cannot pick up the scent shows maternal behaviors in a shorter amount of time. Thus, (D) should be eliminated.


Ah ha... normally, an adult female rat will start showing maternal interest in a pup that she did not bear after about a week. If this maternal interest is normally inhibited by the odor of the pup, we can infer that the time would be shortened if the female could NOT smell the odor of the pup.

For example, if the female's sense of smell has been disabled or if the scent-producing glands of the pup have been removed, the adult female will not be able to smell the pup. This would remove a factor that, according to choice (E), normally inhibits maternal interest. As a result, those maternal interests would be developed in LESS time than usual.

Choice (E) explains the difference described in the passage and is the best answer.

I hope that helps!