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
Mechanism of adhesion of GIC restoration with tooth surface is by means of? 
Select and explain. 
A. Carboxyl group, B. Chelates with Metal Ions, C. C=C double bond, D. Polymer Chains
A: Carboxyl group
Answer: A: Carboxyl group 
Explanation: None