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
Which of the following zones is used for melting alloy during casting: 
Select and explain. 
A. Reducing flame, B. Oxidizing flame, C. Green flame, D. All of the above
A: Reducing flame
Answer: A: Reducing flame 
Explanation: None