This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Epidemiology, Subject name: Social & Preventive Medicine
[{'content': 'Denominator while calculating the secondary attack rate includes- \nSelect and explain. \nA. All the people living in next fifty houses, B. All the close contacts, C. All susceptible among close contacts, D. All susceptible in the whole village', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The denominator consists of all persons who are exposed to the case. More specifically the denominator may be restricted only to susceptible contacts if means are available to distinguish the susceptible persons from the immune. (refer pg no 100 park 23rd edition)', 'role': 'assistant'}]