Q. Which compound is used in contraceptive pills?

Correct Answer: b) Levonorgestrel

Explanation:
– Levonorgestrel is a synthetic progestin widely used in oral contraceptive pills and in emergency contraception. It works mainly by preventing or delaying ovulation and thickening cervical mucus.
– Vanlaflexine (venlafaxine) is an antidepressant (SNRI), not a contraceptive.
– Cholecalciferol is Vitamin D3, used for bone health and vitamin D deficiency.
– Cetrizine (cetirizine) is an antihistamine used for allergies.

Therefore, the correct choice is Levonorgestrel.