This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nervous system, Subject name: Physiology
[{'content': 'Most sensitive nerve fiber to hypoxia \nSelect and explain. \nA. A, B. B, C. C, D. All are equally sensitive', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Question repeated', 'role': 'assistant'}]