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: Pharmacology
[{'content': 'Drug which is useful for the diagnosis of myasthenia gravis is? \nSelect and explain. \nA. Neostigmine, B. Physostigmine, C. Edrophonium, D. Atropine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The\xa0two\xa0types\xa0of weakness\xa0require\xa0opposite\xa0treatments.\xa0They\xa0can\xa0be\xa0differentiated\xa0by edrophonium\xa0test.', 'role': 'assistant'}]