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': '5% NaF in resinous base is: \nSelect and explain. \nA. Duraphat., B. Cavity shield., C. Duraflour., D. Carex', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]