This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Methods - Combined Oestrogen-Progestogen Methods, Subject name: Gynaecology & Obstetrics
[{'content': 'OC pills should be taken on - \nSelect and explain. \nA. 5th day, B. 3rd day, C. 1st day, D. When menses cease', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is 'c' i.e., 1st day", 'role': 'assistant'}]