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 beta (b2) antagonistic: 
Select and explain. 
A. Esmolol, B. Betaxolol, C. Butoxamine, D. Celiprolol
C: Butoxamine
Answer: C: Butoxamine 
Explanation: (Butoxamine): Ref: 125-KDT (136-KDT 6th)CLASSIFICATION OF b ADRENERGIC BLOCKING AGENTSNonselectgive (b1 and b2)Cardio selective (b1)Selective (b2)a. without intrinsic sympatho mimetic activity- Propranolol, sotalol, timololMetoprololButoxamine ICI 118551Atenolol Acebutolol b. With intrinsic sympathomimetic activity- PindololBisoprolol Esmolol Betaxolol c. With additional a blocking property Labetalol, carvediololCarvedilol