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': 'The common cause of bilateral internuclear ophthalmoplegia is: \nSelect and explain. \nA. Multiple sclerosis, B. Lead toxicity, C. Diphtheria, D. Diabetes mellitus', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. Multiple sclerosis', 'role': 'assistant'}]