This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Eye, Nose and Ear, Subject name: Anatomy
[{'content': 'The optic nerve is a tract of the diencephalon that is not completely myelinated until \nSelect and explain. \nA. 5 years after bih, B. 2 years after bih, C. 1 year after bih, D. 3 months after bih', 'role': 'user'}, {'content': 'Answer: D \nExplanation: The axons of the optic nerve are not completely myelinated until 3 months after bih. Myelinated axons are normally not found in the retina. The optic nerve is not a true peripheral nerve but a tract of the diencephalon; when severed, the optic nerve does not regenerate. Myelination in the central nervous system (CNS) is accomplished by oligodendrocytes; oligodendrocytes are not found in the retina.', 'role': 'assistant'}]