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: Radiology
[{'content': 'The best method to reduce radiation caries is application of viscous \nSelect and explain. \nA. 0.5% neutral sodium fluoride gel, B. 1% neutral sodium fluoride gel, C. 0.5% stannous fluoride gel, D. 1% stannous fluoride gel', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]