The Primary Difference Between Estrous and Menstrual Cycles Is That

The primary difference between estrous and menstrual cycles is that ________.

A) the endometrium shed by the uterus during the estrous cycle is reabsorbed with no extensive fluid flow out of the body, whereas the shed endometrium of menstrual cycles is excreted from the body
B) behavioral changes during estrous cycles are much less apparent than those of menstrual cycles
C) season and climate have less pronounced effects on estrous cycles than they do on menstrual cycles
D) copulation normally occurs across the estrous cycle, whereas in menstrual cycles copulation only occurs during the period surrounding ovulation