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': 'Angle of Tip of an endodontic instrument \nSelect and explain. \nA. 75 + 15, B. 75 — 15, C. 75 ± 15°, D. 80°', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]