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 alpha 2 antagonist ? 
Select and explain. 
A. Prazosin, B. Labetalol, C. Yohimbine, D. Butoxamine
C: Yohimbine
Answer: C: Yohimbine 
Explanation: None