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': "Best fLuoride index at 8ppm water level? \nSelect and explain. \nA. Dean's, B. Community FI, C. TFI, D. TSFI", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]