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
Cavity varnish is used for: 
Select and explain. 
A. To reduce thermal conductivity, B. To reduce the permeability of acid into dentinal tubules, C. Action as an obtundant, D. All of the above
B: To reduce the permeability of acid into dentinal tubules
Answer: B: To reduce the permeability of acid into dentinal tubules 
Explanation: None