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
Which of the following is Masochistic habit 
Select and explain. 
A. Nail biting, B. Digit Sucking, C. Lip biting, D. Gingival stripping
D: Gingival stripping
Answer: D: Gingival stripping 
Explanation: Classification of Habits