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 a selective β2 antagonist ? 
Select and explain. 
A. Esmolol, B. Betaxolol, C. Butoxamine, D. Celiprolol
C: Butoxamine
Answer: C: Butoxamine 
Explanation: None