This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Autonomic nervous system, Subject name: Pharmacology
[{'content': 'The following drug is a synthetic choline ester (REPEAT) \nSelect and explain. \nA. Nicotine, B. Pilocarpine, C. Arecoline, D. Carbachol', 'role': 'user'}, {'content': "Answer: D \nExplanation: Remaining all are naturally obtained from plants-alkaloids-the word ends with ''ine'' Ref: KDT 7th ed pg 101", 'role': 'assistant'}]