This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Acute Renal Failure, Subject name: Medicine
Pre-renal azotemia is associated with one of the following characteristic feature: 
Select and explain. 
A. Urinary Na+ < 10 mmol/L, B. Renal failure index > 1, C. Osmolality < 500, D. Urinary creatinine / P. creatinine ratio < 20
A: Urinary Na+ < 10 mmol/L
Answer: A: Urinary Na+ < 10 mmol/L 
Explanation: Ans. is 'a' Urinary Na+ < 10 mmol/litre Explained earlier