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
[{'content': 'Which of the following levels of fluorides in drinking  water is associated with enamel fluorosis? \nSelect and explain. \nA. 0.2 ppm, B. 0.7 ppm, C. 2.5 ppm, D. 1.2 ppm', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]