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
A 26 years old male with restriction of eye movements in all directions and moderate ptosis but with no diplopia or squint. Diagnosis is: 
Select and explain. 
A. Thyroid ophthalmopathy, B. Chronic progressive external ophthalmoplegia, C. Myasthenia gravis, D. Multiple cranial nerve palsies
B: Chronic progressive external ophthalmoplegia
Answer: B: Chronic progressive external ophthalmoplegia 
Explanation: Ans. Chronic progressive external ophthalmoplegia