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
Shoest half life is of ? 
Select and explain. 
A. Metacholine, B. Acetyl choline, C. Carbachol, D. Bethanechol
B: Acetyl choline
Answer: B: Acetyl choline 
Explanation: Ans. is'b'i.e., Acetylcholine Acetylcholine is very rapidly hydrolyzed; large amounts must be infused intravenously to achieve concentrations sufficient to produce detectable effects.Methacholine is more resistant to hydrolysis, and the carbamic acid esters carbachol and bethanechol are still more resistant to hydrolysis by cholinesterase and have correspondingly longer duration of action.