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: Radiology
[{'content': 'Increased bone density is seen in all except - \nSelect and explain. \nA. Primary hyperparathyroidism, B. Osteopetrosis, C. Fluorosis, D. Hypoparathyroidism', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Increased bone density is seen in secondary hyperparathyroidism (not in Primary hyperparathyroidism).', 'role': 'assistant'}]