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
C3b is converted to C3 convertase by 
Select and explain. 
A. Factor D, B. Factor H, C. Factor I, D. All the above
A: Factor D
Answer: A: Factor D 
Explanation: C3b is converted to C3 convertase by Factor B, Factor D, Properdin.