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': 'Titanium casting is done \nSelect and explain. \nA. Under vacuum in argon atmosphere, B. Under air pressure in nitrogen atmosphere, C. In specially fabricated aluminium vanadium crucible, D. Using CAD-CAM technique', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Titanium\xa0has\xa0a\xa0high\xa0melting\xa0point\xa0(1668\xa0°C)\xa0and\xa0high\xa0rate of oxidation above 900 °C. It requires a special casting\xa0machine\xa0with\xa0arc-melting\xa0capability\xa0and\xa0an\xa0argon\xa0atmosphere along with a casting investment consisting of\xa0oxides,\xa0such\xa0as\xa0MgO,\xa0ZrO2,\xa0or\xa0Y2O3,\xa0which\xa0are\xa0more\xa0stable\xa0than\xa0titanium\xa0oxide,\xa0to\xa0ensure\xa0acceptable\xa0castability.\nPhillips 12th edition page 376', 'role': 'assistant'}]