This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: obstetrics,pediatrics and geriatrics, Subject name: Social & Preventive Medicine
[{'content': "Road to health card' top line is - \nSelect and explain. \nA. 3rd percentile, B. 50th percentile, C. 80th percentile, D. 97th percentile", 'role': 'user'}, {'content': "Answer: B \nExplanation: Road to health card top line indicates 50 percentile. REF. PARK'S TEXTBOOK OF PREVENTIVE AND SOCIAL MEDICAL 21ST EDITION. PAGE NO - 502", 'role': 'assistant'}]