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': 'Fejereskov and Thylstrup index is used for \nSelect and explain. \nA. Caries Index in primary teeth, B. Index to measure Fluorosis, C. Gingival Bleeding Index, D. Periodontal Index', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]