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
Low and fixed specific gravity of urine is seen in ? 
Select and explain. 
A. Diabetes mellitus, B. Diabetes insipidus, C. Chronic renal failure, D. Acute glomerulonephritis
C: Chronic renal failure
Answer: C: Chronic renal failure 
Explanation: Ans is 'c' i.e., Chronic renal failure.