15. How many days does menstrual flow usually last? A. 2-7 days B. 4-10 days C. 3-5 days D. 28 days 16. In this stage, hormones are produced to stimulate the growth of ovarian follicles thickening of endometrium. A. Follicular Stage B. Ovulation C. Luteal Stage D. Menstruation 17. In this stage, hormones act on the uterus for the preparation for pregnancy. A. Follicular Stage B. Ovulation C. Luteal Stage D. Menstruation