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 is a Chemoattractant - 
Select and explain. 
A. C5a, B. Cl, C. C3, D. C2
A: C5a
Answer: A: C5a 
Explanation: Ans-C5a* Major opsonins: C3b, IgG, mannose-binding lecithin (MBL), fibronectin, fibrinogen, and CRP.* Membrane attack complex: MAC has a subunit composition of C5b, C6, C7fC8, and polymeric C9* Anaphylatoxin: Both C3a and C5a anaphylatoxin activity.