(c) : $GnRH$ is secreted by the hypothalamus which stimulates the anterior lobe of pituitary gland to secrete luteinising hormone $(LH) $ and $FSH$. $FSH $ stimulates the growth of the ovarian follicles and stimulates the formation of estrogens. $LH$ stimulates the corpus luteum to secrete progesterone. Rising levels of progesterone and estrogen inhibits the release of $GnRH$, which in turn, inhibits the production of $FSH$ and $LH$.