This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Pharmacology
[{'content': 'The progestogenic emergency contraceptive pills act by: \nSelect and explain. \nA. Altered cervical secretion, B. Inhibition of ovulation, C. Anti-implantation effect, D. Inhibition of LH secretion', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The postcoital pill may dislodge a just implanted blastocyst or may interfere with implantation because endometrium is made either hyperproliferative or hypersecretory or atrophic. If it is not the case of emergency contraception, then progesterone could act by increasing the cervical mucus viscosity Ref.Essentials of medical pharmacology TD Tripathi 7th edition page no.324)', 'role': 'assistant'}]