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': 'Uniform reduction on the tooth surface may be ensured by the placement of \nSelect and explain. \nA. Pins, B. Depth grooves, C. Ledges, D. Bevels', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]