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
[{'content': 'Extent of etching should be: \nSelect and explain. \nA. 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', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]