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: Microbiology
[{'content': 'Cytolytic activity of membrane attack complex is modulated by ? \nSelect and explain. \nA. Factor I, B. Factor B, C. Factor S, D. Factor H', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is 'c' i.e., Factor S", 'role': 'assistant'}]