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: Pathology
Causes of nephrocalcinosis are - 
Select and explain. 
A. Hyperparathyroidism, B. T.B. Kidney, C. Hypercalcemia, D. All
D: All
Answer: D: All 
Explanation: Ans. is 'a' i.e., Hyperparathyroidism; 'b' i.e., T.B. Kidney; 'c' i.e., Hypercalcemia