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
Which of the following is common to both zinc eugenol cement and polycarboxylate cement? 
Select and explain. 
A. Polyacrylic acid is liquid, B. Chemical bond to tooth structure, C. Chelation, D. Substitution of eugenol by EBA to increase strength of cement
C: Chelation
Answer: C: Chelation 
Explanation: None