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
[{'content': 'To facilitate the screening of visual-acuity, WHO defines blindness as counting fingers at a distance of: September 2006 and September 2010 \nSelect and explain. \nA. 1 meter, B. 3 meters, C. 6 meters, D. 9 meters', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B: 3 meters The WHO proposed a uniform criterion and defined blindness as "visual acuity of less than 3/ 60 (Smellen) or its equivalent" . In order to facilitate the screening of Visual acuity by non-specialized personnel, in the absence of appropriate vision chas, the WHO has now added the "inability to count fingers in daylight at a distance of 3 meters" to indicate less than 3/60 or its equivalent.', 'role': 'assistant'}]