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 drug which inhibits the rate-limiting step of acetylcholine synthesis is \nSelect and explain. \nA. Vesamicol, B. Hemicholinium, C. Botulinum toxin, D. Cocaine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Rate limiting step is mediated by choline acetyltransferase which is blocked by hemicholinium. Ref: KD T ripathi 8th ed.', 'role': 'assistant'}]