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: Dental
[{'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 susceptibles amongst close contact, D. All susceptibles in the whole village', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]