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
Pinhole is used to neutralize refractive error till 
Select and explain. 
A. 2D, B. 4D, C. 6D, D. 3D
B: 4D
Answer: B: 4D 
Explanation: None