(c) : If the mammalian ovum fails to fertilize choices, (a) and (b) are obvious. since corpus luteum declines so progesterone also decreases rapidly (progesterone is essential for maintenance of pregnancy). Also estrogen continues to cause growth of the endometrium which ultimately becomes thick enough to breakdown and cause menstruation. Hence choice(c) is incorrect as estrogen secretion does not decrease further. Primary follicles continue developing irrespective of ovulatory condition.