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': 'The upper line in the road-to-health card corresponds to: \nSelect and explain. \nA. 95th percentile, B. 50th percentile, C. 3rd percentile, D. 90th prercentile', 'role': 'user'}, {'content': 'Answer: B \nExplanation: 50th percentile', 'role': 'assistant'}]