This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Brain , Subject name: Anatomy
[{'content': 'Myelin sheath in the central nervous system is formed by \nSelect and explain. \nA. Schwann cell, B. Microglia, C. Oligodendrocytes, D. Protoplasmic astrocytes', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Oligodendrocytes are responsible for myelination in the CNS. In the PNS, Schwann cells form the myelin sheath. The process of myelination begins before bih and is not complete until a year or more after bih. (Ref: Vishram Singh textbook of neuroanatomy, second edition, pg- 19)', 'role': 'assistant'}]