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': 'Indications for mucogingival surgery include the following except \nSelect and explain. \nA. A shallow vestibule, B. Insufficient attached gingiva, C. Infrabony pockets, D. A high frenum attachment', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]