This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S, Subject name: Medicine
21 year old female presents with history of mild bilater ptosis, proximal muscle weakness and easy fatiguability which among the following is best in diagnosis this condition 
Select and explain. 
A. Muscle biopsy, B. Edrophonium test, C. Repetitive nerve stimulation, D. Electro myography
B: Edrophonium test
Answer: B: Edrophonium test 
Explanation: * For diagnosis inject edrophonium 2mg i.v Improvement- myasthenic crisis No improvement or worsening - cholinergic crisis. The Tensilon test uses the drug Tensilon (edrophonium) to help your doctor diagnose myasthenia gravis. Tensilon prevents the breakdown of the chemical acetylcholine, a neurotransmitter that nerve cells release to stimulate your muscles. This prevents muscles from being stimulated and makes muscles easy to tire Ref Harrison20th edition pg 2345