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: Pathology
[{'content': 'C3 convertase acts on \nSelect and explain. \nA. C3, B. C4b2b, C. C4b, D. Lymphocytosis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: All 3 pathways of complement system lead to the formation of C3 convertase, which cleaves C3 into C3a and C3b.', 'role': 'assistant'}]