Metabolic acidosis is caused by which of the following?

The principal function of aldosterone is to increase sodium reabsorption in the distal tubule and collecting ducts, which causes secretion of potassium and hydrogen ions.Hypoaldosteronism (e.g., in Addison's disease)therefore results in a decrease in H+ secretion, which leads to the production of metabolic acidosis (and hyperkalemia and hyponatremia).Hypoventilation produces respiratory acidosis.Hypokalemia causes an increase in K+ reabsorption and an increase in H+ secretion, resulting in a metabolic alkalosis.Hypovolemia results in an increase in aldosterone secretion, which can lead to an increase in H+ secretion and a metabolic alkalosis.Hypocalcemia does not directly affect acid-base balance.