This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Environment and health, Subject name: Social & Preventive Medicine
[{'content': 'Dental caries is prevented by - \nSelect and explain. \nA. Iron, B. Fluoride, C. Iodide, D. Iron', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Flourine is most abundant element in nature. Flourine is a double edged sword. Prolonged excess intake results in dental and skeletal flourosis .Inadequate intake result in dental caries.Use of flouride is most effective way of preventing dental caries. Recomended level of flourides in drinking water is 0.5 - 0.8 mg per litre. Parks textbook of preventive and social medicine.K Park. Edition 23.Pg no: 625', 'role': 'assistant'}]