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 β1 selective blocker is used in glaucoma: \nSelect and explain. \nA. Levobunolol, B. Timolol, C. Betaxolol, D. Carteolol', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]