This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Ophthalmology
In a child the normal resolution visual acuity levels such as that of adults i.e. 6/6 is attained by which age? 
Select and explain. 
A. 4 months, B. 1 year, C. 3 years, D. 6 years
D: 6 years
Answer: D: 6 years 
Explanation: .