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
[{'content': 'Most chemotactic propey is with ? \nSelect and explain. \nA. C3a, B. C5a, C. C5-9, D. C3b', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is `b' i.e., C5a C is a powerful chemotactic agent.", 'role': 'assistant'}]