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 of the following is used as a thickening agent in dentrifices? 
Select and explain. 
A. Calcium carbonate, calcium phosphate and calcium sulphate, B. Sodium bicarbonate and aluminium oxide, C. Sodium lauryl sulphate and sodium lauryl succinate, D. Carboxymethyl cellulose and alginate amylase
D: Carboxymethyl cellulose and alginate amylase
Answer: D: Carboxymethyl cellulose and alginate amylase 
Explanation: None