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': 'A 40 year old male patient complains of decayed tooth. Patient gives history of class I cavity preparation and restoration with conventional amalgam with 26. Intra-oral examination reveals proximal caries with 26. The copper content of the restoration done in this patient is?\u200b \nSelect and explain. \nA. 2-5%, B. 6%, C. 12-30%, D. 9%', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Low-copper amalgam alloys contain 2%\u200b to 5% copper. The earliest successful amalgams were\u200b made by combining filings of such alloys with mercury.\u200b A typical modern low-copper amalgam alloy may contain 69.4% Ag, 26.2% Sn, 3.6% Cu, and 0.8% Zn. Amalgams made from such low-copper alloy filings are often referred to as conventional amalgams. High-\u200bcopper amalgam alloys contain 12% to 30% copper, and\u200b because of their higher copper content, they display significantly better corrosion resistance than low-copper\u200b amalgams.\nReference: Sturdevant’s Art and Science of Operative Dentistry, Mosby, 4th Edition, Page No: 149', 'role': 'assistant'}]