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 range of level of fluoride secreted by the glands into the mouth is 
Select and explain. 
A. 0.004-0.005 ppm, B. 0.006-0.007 ppm, C. 0.007-0.05 ppm, D. 0.007-0.08 ppm
C: 0.007-0.05 ppm
Answer: C: 0.007-0.05 ppm 
Explanation: None