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': 'A dental bur cuts the tooth structure more effectively when rake angle of bur is \nSelect and explain. \nA. Positive, B. Negative, C. Radial, D. None of the above', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]