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': 'Most significant angle in bur design \nSelect and explain. \nA. Rake angle, B. Clearance angle, C. Spiral angle, D. Crosscut angle', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]