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 cha was given by - \nSelect and explain. \nA. John snow, B. David Morley, C. Koch, D. Henrey Ducant', 'role': 'user'}, {'content': "Answer: B \nExplanation: Road to health cha was designed by David Morley. REF. PARK'S TEXTBOOK OF PREVENTIVE AND SOCIAL MEDICAL 21ST EDITION. PAGE NO - 502", 'role': 'assistant'}]