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 A: V ratio of retinal blood vessels is: \nSelect and explain. \nA. 1:02, B. 2:03, C. 3:02, D. 3:04', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. 2 : 3', 'role': 'assistant'}]