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': 'The purpose of periodontal dressing is \nSelect and explain. \nA. Prevent overgrowth of granulation tissue, B. Protect the wound from local environmental changes, C. Make the patient comfortable after periodontal surgery, D. All of the above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]