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 principal resin constituent of polishable composite resin is 
Select and explain. 
A. Poly methyl methacrylate, B. Polycarbonates, C. Urethane dimethacrylate, D. Cyanoacrylates
C: Urethane dimethacrylate
Answer: C: Urethane dimethacrylate 
Explanation: None