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: Dental
The % reduction in caries to be expected by the application of neutral fluoride solution is: 
Select and explain. 
A. 20%, B. 20-50%, C. variable, D. 10%
B: 20-50%
Answer: B: 20-50% 
Explanation: None