Concept:Levonorgestrel is a synthetic progestin hormone that acts like natural progesterone to prevent pregnancy.Explanation:Levonorgestrel is widely used in both daily oral contraceptive pills and emergency contraception. It works by stopping ovulation, thickening cervical mucus to block sperm, and altering the uterine lining to prevent implantation. Other options are incorrect: Cholecalciferol is vitamin D, not a contraceptive. Venlafaxine (Vanlaflexine) is an antidepressant. Cetrizine is an antihistamine for allergies. None of these prevent pregnancy.Answer:Option A (Levonorgestrel) is correct.