The correct option is C Estrogen secretion further increases
If the egg is not fertilized, the corpus luteum stops secreting progesterone and decays (after approximately 10 days in humans). It then degenerates into corpus albicans, which is a mass of fibrous scar tissue. Since corpus luteum disintegrates, progesterone levels also decrease rapidly (progesterone is essential for maintenance of pregnancy). Also estrogen continues to cause growth of the endometrium which ultimately becomes thick enough to break down and cause menstruation. Hence this choice is incorrect as estrogen secretion does not increase further. Primary follicles continue developing irrespective of ovulatory condition.