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': 'Measles vaccine is not given before: \nSelect and explain. \nA. 9 months, B. 12 months, C. 15 months, D. 18 months', 'role': 'user'}, {'content': 'Answer: A \nExplanation: 9 months', 'role': 'assistant'}]