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 coupling agent used in composite resin 
Select and explain. 
A. Colloidal silica, B. Urethane dimethacrylate, C. Organo silanes, D. Diketones
C: Organo silanes
Answer: C: Organo silanes 
Explanation: None