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': 'Calcified canal is explored with all of the given instruments except: \nSelect and explain. \nA. 6 K file, B. C+ file, C. 10 K file, D. Profinder', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Canal exploration: 8, 10 K file used.\xa0\nIn calciﬁed canal exploration: 6 K ﬁle, C+ ﬁle, proﬁnder.', 'role': 'assistant'}]