Adult female rats who have never before encountered rat pups will start to show maternal behaviors after being confined with a pup for about seven days. This period can be considerably shortened by disabling the female's sense of smell or by removing the scent-producing glands of the pup.

Which of the following hypotheses best explains the contrast described above?

• AThe sense of smell in adult female rats is more acute than that in rat pups.  
• BThe amount of scent produced by rat pups increases when they are in the presence of a female rat that did not bear them.  
• CFemale rats that have given birth are more affected by olfactory cues than are female rats that have never given birth.  
• DA female rat that has given birth shows maternal behavior toward rat pups that she did not bear more quickly than does a female rat that has never given birth.  
• EThe development of a female rat's maternal interest in a rat pup that she did not bear is inhibited by the odor of the pup.