What Explains the Lack of an Increased Anion Gap Seen

What explains the lack of an increased anion gap seen in metabolic acidosis caused by HCO₃^- loss?

A) For each HCO₃^- ion lost, a Cl^- ion is reabsorbed by the kidney.
B) For each HCO₃^- ion lost, the body produces another to replace it.
C) HCO₃^- is not a measured anion, so its loss does not affect the anion gap.
D) Replacement of HCO₃^- occurs by ammonia ions which are also anions.