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: Ophthalmology
[{'content': 'In optic atrophy pallor of the disc is an index of: \nSelect and explain. \nA. Degeneration of optic nerve fibres, B. Loss of vasculay of the disc, C. Demyelination of the optic nerve fibres, D. All of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. Loss of vasculay of the disc', 'role': 'assistant'}]