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: Surgery
Causes for primary hyperparathyroidism 
Select and explain. 
A. Parathyroid carcinoma, B. Renal failure, C. Rickets, D. Malabsorption
A: Parathyroid carcinoma
Answer: A: Parathyroid carcinoma 
Explanation: None