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
Beta agonist used in bronchial asthma exe their action by- 
Select and explain. 
A. Selective b1 agonism, B. Selective b2 agonism, C. Selective b1 antagonism, D. Selective b2 antagonism
B: Selective b2 agonism
Answer: B: Selective b2 agonism 
Explanation: Ans. is 'b' i.e. Selective b2 agonism