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': "Most common cause of optic neuritis \nSelect and explain. \nA. Ethyl alchol, B. Anterior ischeamic optic neuropathy, C. Leber's disease, D. Multiple sclerosis", 'role': 'user'}, {'content': 'Answer: D \nExplanation: M/C cause - Multiple sclerosis, Vit B12 deficiency, B2 deficiency.', 'role': 'assistant'}]