CBSE Class 12-science Answered

a. Corpus luteum secretes progesterone which is important for the maintenance of endometrium for the implantation of fertilized egg in the uterus. So, corpus luteum is important even though it is the remains of a ruptured follicle. 

b. Progesterone/estrogen can be used as birth control pills. These hormones will inhibit ovulation and thus, prevent conception.

c. Estrogen causes proliferation of endometrium to replace the layer lost during previous menstruation. In this way, it regulates menstrual cycle.

d. FSH stimulates ripening of follicles, maturation of ovum and secretion of estrogen. LH stimulates ovulation, development of corpus luteum and synthesis of progesterone by corpus luteum.