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: Pediatrics
A child with 22-25 stool/day, 3 day old pneumonitis, no passage of urine from 36 hours. low B.P. Blood pH – 7.21. Urine Na+–18 meq/L, S. Urea 120, serum Creatinine 1.2 indicate – 
Select and explain. 
A. Acute cortical necrosis, B. Acute tubular necrosis, C. Pre–renal Azotemia, D. Acute medullary necrosis
C: Pre–renal Azotemia
Answer: C: Pre–renal Azotemia 
Explanation: History and clinical features of the child suggests that he is suffering from acute renal failure. From the given values we have to get the cause of this renal failure.
H/o diarrhea with low BP suggest dehydration —> a cause of prerenal ARE