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': 'Neurological menifestations of fluorosis occur , when the duration of ingestion is: \nSelect and explain. \nA. 10 years, B. 15 years, C. 20 years, D. 25 years.', 'role': 'user'}, {'content': 'Answer: D \nExplanation: The fluoride dosage necessary to produce pathological skeletal fluorosis is estimated to be 20-80 mg/day for a period of 10 to 20 years. In India, it is most commonly seen in Punjab. Neurological Manifestations of fluorosis occur if the duration of ingestion is more than 20 years.', 'role': 'assistant'}]