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
Finn classified habits as: 
Select and explain. 
A. Compulsive and non-compulsive, B. Primary and secondary, C. Useful and harmful habits, D. Both 1 and 2
D: Both 1 and 2
Answer: D: Both 1 and 2 
Explanation: None