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': "Which of the following is not an indicator of significant xerophthalmia problem in community? \nSelect and explain. \nA. Night blindness >1%, B. Bitot's spots >0.05%, C. Corneal ulcer>0.05%, D. None of the above", 'role': 'user'}, {'content': "Answer: D \nExplanation: Criteria Prevalence in 6 month to 6 years population Night blindness >1% Bitot's spots >0.5% Corneal xerosis/ulceration >0.01% Corneal ulcer >0.05% Serum retinol <10 mcg/dl >5% Ref: Park 22nd edition, page 570", 'role': 'assistant'}]