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': 'Hedstrom ﬁle having a double helix cross-section and a variation of the Uniﬁle is: \nSelect and explain. \nA. Hyflex file, B. S-file, C. Unifiles, D. All of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Modification of Hedstrom ﬁle-\nHyﬂex ﬁle. It has a cross-section which presents an “s” shaped instead of the traditional single-helix\xa0 teardrop cross-section of the Hedstrom ﬁle.\nUniﬁles. They are machined from round stainless steel wire by cutting two superﬁcial grooves to\xa0 produce ﬂutes in a double-helix design. They resemble the Hedstrom ﬁle in appearance, are less\xa0 eﬃcient. They are longer marketed\nS-ﬁles. It has a double-helix cross-section and is a variation of the uniﬁle.\nTextbook of Endodontics Nisha GARG 3rd ED', 'role': 'assistant'}]