This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Endocrinology, Subject name: Medicine
Which of the following is associated with secondary hyperparathyroidism - 
Select and explain. 
A. Parathyroid adenoma, B. Marked hypercalcemia, C. Chronic renal failure, D. Parathyroidectomy relieves the symptoms
C: Chronic renal failure
Answer: C: Chronic renal failure 
Explanation: severe secondary hyperparathyroidism occurs due to hypercalcemia associated with renal failure (Harrison 17 pg 2387)