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
The plasticizers used in polyether impression material is: 
Select and explain. 
A. Polyether polymer, B. Colloidal silica, C. Glycol ether, D. Di-vinyl poly (dimethyl siloxane)
C: Glycol ether
Answer: C: Glycol ether 
Explanation: None