This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Central Nervous system, Subject name: Pharmacology
[{'content': 'Carbachol acts as \nSelect and explain. \nA. Agonist for M2 receptors, B. Agonist for M3 receptors, C. Agonist for M1 receptors, D. Antagonist for M3 receptors', 'role': 'user'}, {'content': 'Answer: B \nExplanation: M2 agonist: MethacholineM3 agonists: Carbachol, bethanecholRef: Katzung 12th Ed.Pg 100', 'role': 'assistant'}]