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': 'C-3 convertase in alternate complement pathway - \nSelect and explain. \nA. C4b2a, B. C3b, C. C3bBb, D. C3a', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]