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': 'Which variety of grit should be used to sharpen a dental instrument to be used for tooth preparation? \nSelect and explain. \nA. Very coarse, B. Coarse, C. Medium, D. Fine', 'role': 'user'}, {'content': "Answer: D \nExplanation: Stationary oilstones are available in coarse, medium or ﬁne grit.\xa0\nOnly a ﬁne grit stone is suitable for the ﬁnal sharpening of dental instruments to be used for tooth preparation.\xa0\nCoarse and medium grits may be used for initial reshaping of a badly damaged instrument or for sharpening other dental equipment such as bench knives.\xa0\nCoarser stones cut more rapidly, but produce a rougher surface.\xa0\nIf the use of two or more grits is required, the coarser is used as little as needed for reshaping and then the ﬁnal sharpening is done with a ﬁne stone.\n\nRef: Sturdevant's art and science of operative dentistry. 4th edition page 317", 'role': 'assistant'}]