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
Which of the following serotonergic   receptors is an  autoreceptor? 
Select and explain. 
A. 5-HT1a, B. 5-HT1B/1D, C. 5-HT2a, D. 5-HT
A: 5-HT1a
Answer: A: 5-HT1a 
Explanation: None