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': 'Thickness of smear layer produce by cavity cutting is approximately about: \nSelect and explain. \nA. 0.5 micron thick., B. 1 micron thick., C. 2 micron thick., D. 2.5 micron thick.', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]