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: Ophthalmology
[{'content': 'The first line of treatment of open angle glaucoma is – \nSelect and explain. \nA. Timolol, B. Pilocarpine, C. Epinephrine, D. Carbonic anhydrase inhibitor', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]