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: Physiology
[{'content': 'First change to occur in the distal segment of cut nerve: \nSelect and explain. \nA. Myelin degeneration, B. Axonal degeneration, C. Mitosis of Schwann cell, D. Sprouting', 'role': 'user'}, {'content': 'Answer: B \nExplanation: After\xa0axotomy, the\xa0nerve\xa0terminals\xa0of\xa0the injured neuron begin to degenerate (first).', 'role': 'assistant'}]