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
Which one of the following is not used as an abrasive in the dentifrice 
Select and explain. 
A. Calcium carbonate, B. Silica, C. Sodium Chloride, D. Amylase
D: Amylase
Answer: D: Amylase 
Explanation: None