What Is the Principal Difference Between Menstrual and Estrous Cycles

Multiple Choice

What is the principal difference between menstrual and estrous cycles?

A) The estrous cycle occurs if the female becomes pregnant,whereas the menstrual cycle occurs if the female is not pregnant.
B) The menstrual cycle occurs if the female becomes pregnant,whereas the estrous cycle occurs if the female is not pregnant.
C) The estrous cycle lacks menstruation.
D) The menstrual cycle occurs in mammals,whereas the estrous cycle occurs in birds.
E) Only the menstrual cycle is controlled by estrogen.