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: Social & Preventive Medicine
[{'content': 'The recommended level of fluorides in drinking water in this Country is accepted as \nSelect and explain. \nA. 0.5 to 0.8 mg per litre, B. 1 to 2 mg per litre, C. 3 to 6 mg per litre, D. 7 to 12 mg per litre', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]