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
DMF(s) is defined as: 
Select and explain. 
A. Irreversible index, B. Measures cumulative index, C. Morbidity index, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: None