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': 'MMR Type of vaccine: \nSelect and explain. \nA. Live attenuated, B. Killed, C. Toxoid, D. Subunit', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Live attenuated', 'role': 'assistant'}]