This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: A.N.S., Subject name: Pharmacology
[{'content': 'Shortest acting beta-blocker - \nSelect and explain. \nA. Propranolol, B. Esmolol, C. Timolol, D. Atenolol', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Esmolol o Shortest acting b-blocker - Esmololo Longest acting b-blocker - Nodalol", 'role': 'assistant'}]