Answer: Option B
:
B
The menstrual cycle begins on day 1 with the onset of bleeding, known as menstrual phase or menstruation. It is the shedding of the endometrial lining of the uterus. Every month, in response to the increased FSH, LH, and estrogen during follicular growth and ovulation, the endometrium or lining of the uterus undergoes changes. When fertilization doesn’t take place, the corpus luteum degenerates. This degeneration of the corpus luteum leads to a drop in estrogen and progesterone. When this happens the endometrial lining, which is rich in vasculature and very thick, begins to shed.