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': 'For prevention of retrolental fibroplasia 02 should be: \nSelect and explain. \nA. 30-40%, B. 50-60%, C. 20-30%, D. 70-80%', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. 30-40%', 'role': 'assistant'}]