This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General anatomy, Subject name: Anatomy
[{'content': 'Chemotactic complement component are \nSelect and explain. \nA. C3a, B. C5a, C. Both, D. C3b', 'role': 'user'}, {'content': 'Answer: B \nExplanation: ref Robbins 8/e p64 ;7/ep56;9/e p77.', 'role': 'assistant'}]