This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Fluid and electrolytes, Subject name: Medicine
Which of the following doesn't cause metabolic acidosis- 
Select and explain. 
A. Pyloric stenosis, B. Renal failure, C. Ureterosigmoidostomy, D. Pancreatic Fistula
A: Pyloric stenosis
Answer: A: Pyloric stenosis 
Explanation: Uretrosigmoidostomy and pancreatic fistula causes non anion gap metabolic acidosis, whereas renal failure causes high anion gap acidosis. (Ref: Harrison's principles of internal medicine,19E pg 320)