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': '2% neutral sodium fluoride contains- \nSelect and explain. \nA. 20 g sodium fluoride powder in 1000 ml distilled water, B. 20 mg sodium fluoride powder in 1000 ml distilled water, C. 20 g sodium fluoride powder in 100 ml distilled water, D. 20 mg sodium fluoride powder in 100 ml distilled water', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Method of preparation of 2% neutral sodium fluoride:\nIt is prepared by dissolving 20 grams of sodium fluoride powder in one liter (1000 ml) of distilled\xa0 water in a plastic bottle. It is\xa0essential to store fluoride in plastic bottles because if stored in glass containers, the fluoride ion of solution can react with silica of glass forming silicon fluoride, thus reducing the availability of free active fluorides for anticaries action.', 'role': 'assistant'}]