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
Setting reaction of solution liners: 
Select and explain. 
A. Chemical reaction, B. Physical evaporation, C. Both of the above, D. None
B: Physical evaporation
Answer: B: Physical evaporation 
Explanation: Solution Liners
Based on non aqueous solution of acetone, alcohol or ether. Eg: Varnish (COPAL WASH).
Composition:

10% copal resin.
90% solvent.

Setting reaction: Physical evaporation.

Thin film; copal resin remains.
Single layer of varnish covers 55% of surface area.
If 2-3 layers are applied; 6-80% area is covered.