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, the optic disc appears pale, is index of- \nSelect and explain. \nA. Atrophy of the nerve fibre, B. Loss of vasculature, C. Gliosis, D. All of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Disappearance of vascularity of the disc causes increase in pallor.', 'role': 'assistant'}]