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
Extent of etching should be: 
Select and explain. 
A. 0.2 mm beyond the preparation, B. 0.5 mm beyond the preparation, C. 1.0 mm beyond the preparation, D. Any of the above
B: 0.5 mm beyond the preparation
Answer: B: 0.5 mm beyond the preparation 
Explanation: None