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
The following drug is a synthetic choline ester (REPEAT) 
Select and explain. 
A. Nicotine, B. Pilocarpine, C. Arecoline, D. Carbachol
D: Carbachol
Answer: D: Carbachol 
Explanation: Remaining all are naturally obtained from plants-alkaloids-the word ends with ''ine'' Ref: KDT 7th ed pg 101