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: Physiology
In which of the following condition normal anion gap metabolic acidosis is seen? 
Select and explain. 
A. Diarrhoea, B. Renal failure, C. Lactic acidosis, D. Diabetic ketoacidosis
A: Diarrhoea
Answer: A: Diarrhoea 
Explanation: Alkali can be lost from the gastrointestinal tract in diarrhea or from the kidneys (renal tubular acidosis, A). In these disorders, reciprocal changes in and result in a normal anion gap. In pure non-AG acidosis, therefore, the increase in above the normal value approximates the decrease in . Causes of non anion gap acidosis: Gastrointestinal bicarbonate loss Diarrhea External pancreatic or small-bowel drainage Ureterosigmoidostomy, jejunal loop, ileal loop Drugs Calcium chloride (acidifying agent) Magnesium sulfate (diarrhea) Cholestyramine (bile acid diarrhea) Renal acidosis Hypokalemia Hyperkalemia Drug-induced hyperkalemia (with renal insufficiency) Potassium-sparing diuretics (amiloride, triamterene, spironolactone) Trimethoprim ACEIs and ARBs Nonsteroidal anti-inflammatory drugs Other Loss of potential bicarbonate: ketosis with ketone excretion Cation exchange resins Ref: DuBose, T.D. (2012). Chapter 47. Acidosis and Alkalosis. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e.