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': 'Unmyelinated fibers differ from myelinated fibers in that they: \nSelect and explain. \nA. Have increased excitability, B. Have no nodes of Ranvier, C. Have no power of regeneration, D. Have no association of Schwann cells', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]