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 objectives for the extension of the proximal margins are all except: \nSelect and explain. \nA. Include all caries lesions, defects or existing restorative materials, B. Create 90-degree cavosurface margins, C. Establish not more than 0.5 mm clearance with the adjacent proximal surface facially, lingually and gingivally, D. The location of the final proximal margins should be established with No.245 bur', 'role': 'user'}, {'content': 'Answer: D \nExplanation: The objectives for the extension of the proximal margins are to:\n\nInclude all caries lesion, defects or existing restorative material.\nCreate approximately 90o\xa0cavosurface margins\xa0(i.e.,\xa0butt-joint margins).\xa0\nEstablish (ideally) not more than 0.5 mm clearance with\xa0the\xa0adjacent\xa0proximal\xa0surface\xa0facially,\xa0lingually,\xa0and gingivally.\n\nThe location of the final proximal margins (i.e., facial, lingual, gingival) should be established with hand instruments (i.e., chisels, hatchets, trimmers) and not the No.245 bur, so as to prevent unnecessary overextension.\nReference: Sturdevant operative dentistry. 7th EDITION,\xa0 Page No:341', 'role': 'assistant'}]