What is the function of corpus luteum?

The correct answer is Option (1) → Secretion of progesterone

Option (1) Secretion of progesterone — Correct. After ovulation, the remains of the Graafian follicle form the corpus luteum. It secretes large amounts of progesterone, which maintains the endometrium for implantation.

NCERT Extract:
Menstrual Cycle – “… The ovulation (ovulatory phase) is followed by the luteal phase during which the remaining parts of the Graafian follicle transform as the corpus luteum (Figure 2.9). The corpus luteum secretes large amounts of progesterone which is essential for maintenance of the endometrium.”