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 concentration of NaF in a daily mouth rinse is: 
Select and explain. 
A. 0.20%, B. 0.05%, C. 0.03%, D. 0.01%
B: 0.05%
Answer: B: 0.05% 
Explanation: None