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': 'A 26 years old male with restriction of eye movements in all directions and moderate ptosis but with no diplopia or squint. Diagnosis is: \nSelect and explain. \nA. Thyroid ophthalmopathy, B. Chronic progressive external ophthalmoplegia, C. Myasthenia gravis, D. Multiple cranial nerve palsies', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. Chronic progressive external ophthalmoplegia', 'role': 'assistant'}]