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': 'First case that comes to notice of physician is ? \nSelect and explain. \nA. Primary case, B. Secondary case, C. Index case, D. Refer case', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is 'c' i.e., Index case o Primary case --> First case of communicable disease introduced into the population. o Index case --> First case to come to attention of the investigator.", 'role': 'assistant'}]