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
After brushing dryness of mouth is caused by 
Select and explain. 
A. Glycol, B. sodium Lauryl sulphate, C. Friction due to brushing, D. Sweetner
B: sodium Lauryl sulphate
Answer: B: sodium Lauryl sulphate 
Explanation: None