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 used in an ameliorative test for myasthenia gravis is: \nSelect and explain. \nA. Physostigmine, B. Edrophonium, C. Tacrine, D. Pyridostigmine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Drug used in ameliorative test (tensilon test) for myasthenia gravis is edrophonium. It is a cholinergic drug and can be used for diagnosis of myasthenia gravis because of its short duration of action (10 - 30 min.)', 'role': 'assistant'}]