This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Excretory System (Kidney, Bladder) Acid-Base Balance, Subject name: Physiology
True about Anion Gap: 
Select and explain. 
A. It is difference between unmeasured anions and unmeasured cations, B. Normal value is 20 mEq/L, C. In Diarrhoea anion gap is increased, D. Anion gap will increase if increases
A: It is difference between unmeasured anions and unmeasured cations
Answer: A: It is difference between unmeasured anions and unmeasured cations 
Explanation: The cation normally measured is Na+, and the anions are usually Cl- and HCO3-. The "anion gap" is the difference between unmeasured anions and unmeasured cations and is estimated as Normal range: 8-16 mEq/L Increase in chloride ion will decrease anion gap Increased Anion Gap (Normochloremia) Normal Anion Gap (Hyperchloremia) Diabetes mellitus ketoacidosis) Diarrhea Lactic acidosis Renal tubular acidosis Chronic renal failure Carbonic anhydrase inhibitors Aspirin (acetylsalicyclic acid) poisoning Addison's disease Methanol poisoning Ethylene glycol poisoning Starvation