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': "The WHO index for fluorosis is based on: \nSelect and explain. \nA. Dean's index, B. McKay's index, C. Community Fluorosis index, D. Public Health fluorosis index", 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]