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: Social & Preventive Medicine
[{'content': 'Best contraceptive for 22 year old married nulliparous women \nSelect and explain. \nA. Condom, B. OCPs, C. Tubectomy, D. Rhythm method', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]