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
C3 convertase acts on 
Select and explain. 
A. C3, B. C4b2b, C. C4b, D. Lymphocytosis
A: C3
Answer: A: C3 
Explanation: All 3 pathways of complement system lead to the formation of C3 convertase, which cleaves C3 into C3a and C3b.