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
Which is the most potent chemotactic complement? 
Select and explain. 
A. C5b, B. C5a, C. C4a, D. C2b
B: C5a
Answer: B: C5a 
Explanation: C5a, C3a, C4a are chemotactic, C5a is most potent chemotactic.