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 most recent direct filling gold which produces the hardest surface on condensation is \nSelect and explain. \nA. Mat gold, B. Encapsulated powered gold, C. Mat gold alloyed with calcium and wrapped in gold foil, D. Platinized gold', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Mat\xa0gold\xa0made\xa0of\xa0electrolytic\xa0precipitate\xa0from\xa0gold, which is alloyed with a trace amount of calcium, can\xa0yield a further increase in hardness by dispersion strengthening without affecting the handling properties.', 'role': 'assistant'}]