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 OHI-S index developed by Greene and Vermillion is
used to measure 
Select and explain. 
A. Dental caries, B. Gingivitis, C. Oral debris and calculus, D. Periodontal disease
C: Oral debris and calculus
Answer: C: Oral debris and calculus 
Explanation: None