A.

progesterone

Progesterone - Supports pregnancy.

FSH Stimulates gonadal activity called as gonadotrophins.

Oxytocin Stimulates contraction in the uterus during childbirth.

Vasopressin Stimulates resorption of water and electrolytes by the distal tubules also called as Antidiuretic Hormone (ADH).

D.

Spermatogonia, spermatozoa, Spermatocyte, Spermatid

Spermatogonia --> Spermatocyte ---> Spermatid --> Spermatozoa

Spermatogonia are present on the inside wall of seminiferous tubule multiplied by mitotic division and an increase in number. Spermatocytes are some of the spermatogonia, which periodically undergo meiosis. The secondary spermatocytes undergo the second meiotic division to produce four, equal haploid spermatids, The spermatids are transformed into spermatozoa. (Sperm)

B.

LH and FSH decrease gradually during the follicular phase

In follicular phase of menstrual cycle. LH and FSH increase gradually and stimulate follicular development as well as secretion of estrogens by the growing follicles. 

B.

by abstaining from coitus from day 10-17 of the menstrual cycle. 

one of the legal methods of birth control is periodic in which couple abstain from coitus from day 10 to 17 of the menstrual cycle.
abortion by taking medicine is not a legal method. A daybreak coitus may increase the chances of contraception.

A.

the ovum and sperms are transported simultaneously to ampullary -isthmic junction of the fallopian tube

Fertilisation is possible only if the sperms and ovum are transported simultaneously at ampullary-isthmic junction of fallopian tube.