In a patient with chronic metabolic acidosis, which of the following mechanisms is most crucial for the kidney to excrete excess acid and regenerate bicarbonate?

✓ Correct Answer: Option C

In chronic acidosis, the kidney significantly increases ammonium production from glutamine. NH4+ acts as a buffer for secreted H+ and is excreted, while the remaining bicarbonate from glutamine metabolism is reabsorbed, effectively regenerating bicarbonate.