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': 'In school water fluoridation, amount of F used is: \nSelect and explain. \nA. 0.7-1.2 ppm, B. 1.6-3 ppm, C. 3-4 ppm, D. 12 ppm', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]