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': 'Among the following longest acting ocular beta-blocker is: \nSelect and explain. \nA. Betaxolol., B. Timolol., C. Cartiolol., D. Metoprolol.', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Betaxolol is a cardioselective beta-blocker which can be used for the treatment of glaucoma.', 'role': 'assistant'}]