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
[{'content': 'The OHI-S index developed by Greene and Vermillion is\nused to measure \nSelect and explain. \nA. Dental caries, B. Gingivitis, C. Oral debris and calculus, D. Periodontal disease', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]