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 bronchodilator ? 
Select and explain. 
A. Corticosteroids, B. Salmeterol, C. Ketotifen, D. Sodium cromoglycate
B: Salmeterol
Answer: B: Salmeterol 
Explanation: None