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
All of the following are ganglion blockers, except 
Select and explain. 
A. Hexamethonium, B. Tropicamide, C. Trimethaphan, D. Mecamylamine
B: Tropicamide
Answer: B: Tropicamide 
Explanation: Tropicamide is a muscarine receptor antagonist used for ophthalmological examination.
Rest three are nicotine receptor antagonists (Nm) which are "Ganglion blockers".