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 5-HT receptors are heptahelical serpentine receptors EXCEPT: 
Select and explain. 
A. 5-HT1, B. 5-HT2, C. 5-HT3, D. 5-HT4
C: 5-HT3
Answer: C: 5-HT3 
Explanation: All serotonin receptors are G-protein coupled receptors except 5-HT3 which is an inotropic receptor.