This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
[{'content': 'OCP failure by rifampicin is due to - \nSelect and explain. \nA. Decreased absorption of OCP, B. Increased binding of OCPs by rifampicin and reduced free drug concentration, C. Increased metabolism of drug, D. Increased chances of ovulation due to rifampicin', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is 'c' i.e., Increased metabolism of drug", 'role': 'assistant'}]