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
The purpose of periodontal dressing is 
Select and explain. 
A. 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
D: All of the above
Answer: D: All of the above 
Explanation: None