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
[{'content': 'Beta agonist used in bronchial asthma exe their action by- \nSelect and explain. \nA. Selective b1 agonism, B. Selective b2 agonism, C. Selective b1 antagonism, D. Selective b2 antagonism', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e. Selective b2 agonism", 'role': 'assistant'}]