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
Sodium lauryi sulphate used in the toothpaste is 
Select and explain. 
A. Humectant, B. Abrasive, C. Flavouring agent, D. Surfactant
D: Surfactant
Answer: D: Surfactant 
Explanation: None