This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Asthma, Subject name: Pharmacology
Which of the following is a long acting beta 2 agonist? 
Select and explain. 
A. Salbutamol, B. Salmeterol, C. Terbutaline, D. Levalbuterol
B: Salmeterol
Answer: B: Salmeterol 
Explanation: Ans. (b) SalmeterolRef.: KDT 6thed /127, 128