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 chemical used to etch enamel is 
Select and explain. 
A. Zinc oxide, B. methyl methacrylate, C. phosphoric acid, D. eugenol
C: phosphoric acid
Answer: C: phosphoric acid 
Explanation: None