This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Non communicable diseases, Subject name: Social & Preventive Medicine
[{'content': 'According to WHO , blindness is defined as a visual acuity of the better eye, less than - \nSelect and explain. \nA. Jun-60, B. May-60, C. Apr-60, D. Mar-60', 'role': 'user'}, {'content': 'Answer: D \nExplanation: <p> WHO defines blindness if the visual acuity is less than 3/60. Reference:Park&;s textbook of preventive and social medicine,K.Park,23rd edition,page no:401. <\\p>', 'role': 'assistant'}]