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': 'Normal Cup : disc ratio of optic disc is \nSelect and explain. \nA. 0.3 to 0.4, B. 0.2 to 0.3, C. 0.5 to 0.6, D. 0.1 to 0.3', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Normal Cup : disc ratio of optic disc\xa00.3 to 0.4.', 'role': 'assistant'}]