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 6 of Russet's index is? \nSelect and explain. \nA. 1/2 bone loss and 1/2 root involvement, B. Advanced bone loss, 1/2root involved, C. Calculus, D. Mild gingivitis", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]