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': 'Polishing agent for amalgam \nSelect and explain. \nA. Tin oxide, B. Iron oxide, C. Alumina, D. Silica', 'role': 'user'}, {'content': 'Answer: A \nExplanation: TIN OXIDE:\nThis extremely fine abrasive material is used extensively as a polishing agent for polishing teeth and metallic restorations such as dental amalgams in the mouth. It is mixed with water, alcohol\xa0or glycerin to form a mildly abrasive paste.\nPhillips Science of Dental Material 12th Edition Page. 245-246.', 'role': 'assistant'}]