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
The most likely diagnosis in a 25 year old male having generalized restriction of eye movement in all direction, intermittent ptosis, proximal muscle weakness, fatiguability. The most useful test is: 
Select and explain. 
A. CPK, B. Edrophoneium test, C. EMG, D. Muscle biopsy
B: Edrophoneium test
Answer: B: Edrophoneium test 
Explanation: Edrophoneium test