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: Social & Preventive Medicine
According to WHO, blindness is defined as a visual acuity of the better eye, less than 
Select and explain. 
A. 6/60., B. 5/60., C. 4/60., D. 3/60.
D: 3/60.
Answer: D: 3/60. 
Explanation: Blindness

WHO has proposed a uniform criterion and defined blindness as "Visual acuity of less than 3/60 or its equivalent".
In the absence of appropriate vision charts, the WHO has now added the "inability to count fingers in daylight at a distance of 3 meters" to indicates less than 3/60 or its equivalent.