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': 'Which of the following serotonergic   receptors is an  autoreceptor? \nSelect and explain. \nA. 5-HT1a, B. 5-HT1B/1D, C. 5-HT2a, D. 5-HT', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]