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
Acid etching of enamel margins 
Select and explain. 
A. Provides chemical retention, B. Provides mechanical retention, C. Is used as resistance form, D. Is used for pulp protection
B: Provides mechanical retention
Answer: B: Provides mechanical retention 
Explanation: None