Q. If mammalian ovum fails to get fertilized, which one of the following is unlikely ?
(a) corpus luteum will degenerate
(b) progesterone secretion rapidly declines
(c) estrogen secretion further decreases
(d) primary follicle starts developing
Option C is the correct answer i.e., Estrogen secretion further decreases
Decrease of estrogen is unlikely to occur when mammalian ovum fails to get fertilized.
As the secondary oocyte is not get fertilized, it is destined to release out of the female body. It will lead to the initiation of second menstruation cycle where gonadotrophins stimulate the oogonium cell to release estrogen. So the level of estrogen increases not decreases.