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 vaccine is recommended at the age of: \nSelect and explain. \nA. 9-12 months, B. 2-3 years, C. 10-19 years, D. 15-18 months', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]