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
Drug used in an ameliorative test for myasthenia gravis is: 
Select and explain. 
A. Physostigmine, B. Edrophonium, C. Tacrine, D. Pyridostigmine
B: Edrophonium
Answer: B: Edrophonium 
Explanation: 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.)