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 is an selective a 2 antagonist? \nSelect and explain. \nA. Prazosin, B. Labetalol, C. Yohimbine, D. Butoxamine', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is 'c' i.e., Yohimbine Selective a2-antagonists are yohimbine and idozoxon.", 'role': 'assistant'}]