(a) A - Estrogen, B - Progesterone.

 

(b) Hormone estrogen is released by ovarian follicle and progesterone is secreted by corpus luteum.

 

(c) During female reproductive cycle, oogonia undergo various developmental stages. Oogonia divides by mitosis to form primary oocytes, which sequentially forms primary follicle, secondary follicle, tertiary follicle and mature Graafian follicle. Graafian follicle secretes hormone estrogen and secondary oocyte is released when LH induces rupturing of Graafian follicle. The remaining part of Graafian follicle develops into corpus luteum which secretes progesterone. As the Graafian follicle forms prior to corpus luteum, therefore, A peaks before B.

 

(d) A (estrogen) stimulates the proliferation of endometrium of the uterine wall after its break down during menstrual phase while B (progesterone) is required for maintaining endometrium which is necessary for implantation of fertilised ovum. It helps to maintain pregnancy.

 

(e) Level of hormone B would remain high on 28th day, if fertilisation occurs. In case of fertilisation, corpus luteum would be maintained for long time to support pregnancy.