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': 'Recommended flouride concentration in water to prevent caries is: March 2010 \nSelect and explain. \nA. 0, B. 0.5 ppm, C. 1ppm, D. 1.5 ppm', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. C: 1ppm Water fluoridation is the process of adding fluoride to the water supply so that the level reaches approximately 1 pa fluoride per million pas water (ppm) or 1 milligram fluoride per liter of water (mg/ L); this is the optimal level for preventing tooth decay.', 'role': 'assistant'}]