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 is an selective a 2 antagonist? 
Select and explain. 
A. Prazosin, B. Labetalol, C. Yohimbine, D. Butoxamine
C: Yohimbine
Answer: C: Yohimbine 
Explanation: Ans. is 'c' i.e., Yohimbine Selective a2-antagonists are yohimbine and idozoxon.