<prompt> Fluoride is added to drinking water in the form of:Hydrofluosilicic acidFluoride ionsAPFNone of the above  <response>: Fluoride compounds used in water fluoridationFluorspar Sodium fluoride Silicofluoride Sodium silicofluoride Ammonium silicofluoride Hydrofluosilicic acid.Essentials of preventive and community dentistrySoben Peter page no. 268 