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': 'Child survival index is calculated by \nSelect and explain. \nA. 1000-IMR/100, B. IMR-1000/10, C. 1000-U5MR/10, D. U5MR-1000/10', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ref:Park's Text book of Preventive and Social Medicine 25th ed", 'role': 'assistant'}]