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
0.05% of NaF has concentration of F 
Select and explain. 
A. 9000 ppm, B. 1000 ppm, C. 225 ppm, D. 250 ppm
C: 225 ppm
Answer: C: 225 ppm 
Explanation: None