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': 'Dental caries is associated with flouride levels in water below: \nSelect and explain. \nA. 0.1 mg, B. 0.5 mg /L., C. 1.0 mg /L, D. 2.0 mg /L', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]