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
Which of the following levels of fluorides in drinking  water is associated with enamel fluorosis? 
Select and explain. 
A. 0.2 ppm, B. 0.7 ppm, C. 2.5 ppm, D. 1.2 ppm
C: 2.5 ppm
Answer: C: 2.5 ppm 
Explanation: None