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': 'Score of 8 on the Russel periodontal index shows: \nSelect and explain. \nA. Irreversible terminal disease, B. Established destructive periodontal disease, C. Beginning destructive periodontal disease, D. Advanced destructive periodontal disease with loss of masticatory function', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]