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': 'Which of the following sympathominetic agents is the most bronchodilator \nSelect and explain. \nA. Amphetamine, B. Nor epinephrine, C. Isoproterenol, D. Phenylephrine', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]