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': 'First instrument inserted into the root canal through the access cavity is \nSelect and explain. \nA. Barbed broach, B. H file, C. K file, D. Any of the above', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]