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': 'Fluoride in any form is contraindicated in: \nSelect and explain. \nA. Chronic renal failure, B. Osteoporosis, C. Hypertension, D. Thyrotoxicosis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]