This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Nerve, Subject name: Physiology
[{'content': 'Myelin in CNS is formed by: \nSelect and explain. \nA. Oligodendrocytes, B. Schwann cells, C. Microglia, D. Astrocytes', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Myelin sheath in the CNS is formed by the oligodendrocytes; Myelin sheath of the peripheral nerves is formed by the Schwann cells.', 'role': 'assistant'}]