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': 'The first instrument to extirpate pulp is \nSelect and explain. \nA. Barbed broach, B. K-type file, C. Reamer, D. H-type file', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]