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
Which of the following is not an indicator of significant xerophthalmia problem in community? 
Select and explain. 
A. Night blindness >1%, B. Bitot's spots >0.05%, C. Corneal ulcer>0.05%, D. None of the above
D: None of the above
Answer: D: None of the above 
Explanation: 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