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 zone is the hottest and efficient burning zone of the flame used for casting? 
Select and explain. 
A. Oxidizing zone, B. Reducing zone, C. Combustion zone, D. None of the above
B: Reducing zone
Answer: B: Reducing zone 
Explanation: None