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: Surgery
[{'content': 'Which of the following technique can be used only in edentulous maxilla to treat oro-antral fistula? \nSelect and explain. \nA. Rehrmann Flap, B. Ashley Flap, C. Bridge Flap, D. Burger Flap', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]