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': 'Periodontal index is also known as: \nSelect and explain. \nA. Loe & Sillness index, B. Russel index, C. Ramford index, D. Shick & ash index', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]