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
Enamel is permeable to? 
Select and explain. 
A. Bacteria, B. Bacterial product, C. Retroviruses, D. Peroxidase
D: Peroxidase
Answer: D: Peroxidase 
Explanation: None