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
Increased bone density is seen in all except - 
Select and explain. 
A. Primary hyperparathyroidism, B. Osteopetrosis, C. Fluorosis, D. Hypoparathyroidism
A: Primary hyperparathyroidism
Answer: A: Primary hyperparathyroidism 
Explanation: Increased bone density is seen in secondary hyperparathyroidism (not in Primary hyperparathyroidism).