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 ophthalmic affection of diphtheria is: \nSelect and explain. \nA. Ptosis, B. Isolated ocular palsies, C. Total ophthalmoplegia, D. Ophthalmoplegia externa', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. Isolated ocular palsies', 'role': 'assistant'}]