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
Dunning index? 
Select and explain. 
A. Gingival bone count, B. Shick & ash, C. OHI, D. PDI
A: Gingival bone count
Answer: A: Gingival bone count 
Explanation: None