This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pharmacokinetics, Subject name: Pharmacology
[{'content': 'Effect of oral contraceptive pills is inhibited by : \nSelect and explain. \nA. Rifampicin, B. Cimetidine, C. Ethambutol, D. Propranolol', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e. Rifampicin", 'role': 'assistant'}]