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': 'Fluoride is added to drinking water in the form of: \nSelect and explain. \nA. Hydroﬂuosilicic acid, B. Fluoride ions, C. APF, D. None of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Fluoride compounds used in water fluoridation\n\nFluorspar\xa0\nSodium fluoride\xa0\nSilicofluoride\xa0\nSodium silicofluoride\xa0\nAmmonium silicofluoride\xa0\nHydrofluosilicic acid.\n\nEssentials of preventive and community dentistry\nSoben Peter page no. 268', 'role': 'assistant'}]