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
For prevention of retrolental fibroplasia 02 should be: 
Select and explain. 
A. 30-40%, B. 50-60%, C. 20-30%, D. 70-80%
A: 30-40%
Answer: A: 30-40% 
Explanation: Ans. 30-40%