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': 'The recommended concentration of acidulated phosphate (APF) ﬂuoride gel is: \nSelect and explain. \nA. 2%, B. 8%, C. 1.23%, D. 10%', 'role': 'user'}, {'content': "Answer: C \nExplanation: An aqueous solution of acidulated phosphate fluoride is prepared by dissolving 20 grams of sodium fluoride in 1 liter of 0.1\xa0M phosphoric acid and to this is added 50% hydrofluoric acid to adjust the pH at 3.0 and fluoride ion concentration at 1.23%.\nIt is also called as\xa0Brudevold's solution.\n\nEssentials of preventive and community dentistry\nSoben Peter\n5th edition\npage no. 258", 'role': 'assistant'}]