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': 'Upper reference curve in growth cha is: \nSelect and explain. \nA. 50th percentile, B. 60th percentile, C. 70th percentile, D. 80th percentile', 'role': 'user'}, {'content': 'Answer: A \nExplanation: 50th percentile', 'role': 'assistant'}]