This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: A.N.S., 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 o Selective a2-antagonists are yohimbine and idozoxon.Important a adrenergic blocking drugso Non equilibrium (irreversible) type - Phenoxybenzamineo Equilibrium (reversible) typeA. Non selective - Ergotamine, Ergotoxine, Tolazoline, Phentolamine, Chlorpromazine,B. a1 selective - Prazosin, Terazosin, Doxazosin, Trimazosin, Alfuzosin, Indoramine, Urapidil, Tamsulosine.C. a2 selective - Yohimbine, Idazoxan