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: Medicine
Xerophthalmia is a public health problem if prevalence of bitot spots is 
Select and explain. 
A. > 1%, B. >0.5%, C. > 0.01%, D. > 0.05%
B: >0.5%
Answer: B: >0.5% 
Explanation: Night blindness : > 1%.
Bitot spots : >0.5%.
Corneal ulcer : >0.05%.
Corneal xerosis : >0.01%.