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
Normal anion-gap metabolic acidosis is seen in - 
Select and explain. 
A. Addison's disease, B. Diabetic ketoacidosis, C. Renal failure, D. lactic acidosis
A: Addison's disease
Answer: A: Addison's disease 
Explanation: The normal value for the serum anion gap is 8-16 mEq/L. However, there are always unmeasurable anions, so an anion gap of less than 11 mEq/L using any of the equations listed in Description is considered normal. For the urine anion gap, the most prominently unmeasured anion is ammonia. Seen in Addison's disease Ref Davidson 23rd edition pg 364