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
[{'content': 'All of the following are ganglion blockers, except \nSelect and explain. \nA. Hexamethonium, B. Tropicamide, C. Trimethaphan, D. Mecamylamine', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Tropicamide is a muscarine receptor antagonist used for ophthalmological examination.\nRest three are nicotine receptor antagonists (Nm) which are "Ganglion blockers".', 'role': 'assistant'}]