This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Kidney, Subject name: Medicine
True about pre renal azotemia - 
Select and explain. 
A. Urine output < 500 ml, B. Urinary cr. / Plasma cr. > 40, C. FeNa< 1, D. FeNa> 1
A: Urine output < 500 ml
Answer: A: Urine output < 500 ml 
Explanation: Prerenal azotemia Oliguria (urine volume < 500 mL/day) or anuria (< 100 mL/day), high urine specific gravity (>1.015), normal urinary sediment, and low urinary sodium (< 20 mEq/L; fractional excretion of sodium < 1%) are seen Ref Harrison20th edition pg 298