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: Unknown
Which of the following components is a potent neutrophil chemotactic agent? 
Select and explain. 
A. C 1, B. C 2, C. C5a, D. C789 complex
C: C5a
Answer: C: C5a 
Explanation: C5a promotes chemotaxis. The complement components C l, C2, and the C789 complex do not promote chemotaxis.