Respiratory acidosis

What is the primary compensatory mechanism in the body for respiratory acidosis?

1: Increased renal excretion of bicarbonate (HCO 3 - )
2: Increased renal reabsorption and decreased excretion of bicarbonate (HCO 3 - )
3: Hyperventilation to reduce carbon dioxide (CO 2 )
4: Decreased renal excretion and increased reabsorption of hydrogen ions (H + )