This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Obstetrics, Subject name: Social & Preventive Medicine
Mechanism of action of Combined OCP pills: 
Select and explain. 
A. Prevent fertilization, B. Prevent release of ovum from ovary, C. Prevent implantation of fertilized ovum, D. Reduce sperm motility
B: Prevent release of ovum from ovary
Answer: B: Prevent release of ovum from ovary 
Explanation: Ans. (b) Prevent release of ovum from ovaryRef: K. Park 23rded. /501* Combined oral contraceptive pills act by inhibiting ovulation by suppressing the release of gonadotropins.* Continuous progesterone by OCPs which give negative feedback to GnRH, which decreases LH release and upto some extent FSH release also.* This prevents LH surge and as a result inhibits ovulation.