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
10% KNO3 is used to 
Select and explain. 
A. treat hypersensitive dentin, B. reduce caries, C. as an acid etchant, D. as a base below restoration
A: treat hypersensitive dentin
Answer: A: treat hypersensitive dentin 
Explanation: None