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': 'Which zone is the hottest and efficient burning zone of the flame used for casting? \nSelect and explain. \nA. Oxidizing zone, B. Reducing zone, C. Combustion zone, D. None of the above', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]