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
Titanium casting is done: 
Select and explain. 
A. Under vacuum in argon atmosphere, B. Under air pressure in nitrogen atmosphere, C. In specially fabricated aluminum vanadium crucibles, D. Using CAD-CAM technique
A: Under vacuum in argon atmosphere
Answer: A: Under vacuum in argon atmosphere 
Explanation: None