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': 'Patient presents with intermittent weakness in proximal group of muscles, fatigubility, ptosis. Which of the following is most definite test to detect the abnormality \nSelect and explain. \nA. Muscle biopsy, B. CPK, C. Endrophonium test, D. EMG', 'role': 'user'}, {'content': 'Answer: C \nExplanation: C i.e. Endrophonium test', 'role': 'assistant'}]