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: Medicine
The commonest cause of chronic renal failure is 
Select and explain. 
A. Chronic glomerulonephritis, B. Chronic pyelonephritis, C. Multiple myeloma, D. Subacute bacterial endocarditis
B: Chronic pyelonephritis
Answer: B: Chronic pyelonephritis 
Explanation: Commonest cause of chronic renal failure is pyelonephritis.