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
Methacholine acts at which receptor? 
Select and explain. 
A. M1, B. M2, C. M3, D. M4
B: M2
Answer: B: M2 
Explanation: Ans: B. M2Methacholine is an M2 receptor agonist.ParameterM1M2M3Agonists (Relatively selective)Oxotremorine, MCN-343AMethacholineBethanecholAntagonists (Relatively selective)Pirenzepine, TelenzepineMethoctramine, TripitramineDarifenacin, Solifenacin