Concept:The kidneys regulate blood composition and remove metabolic wastes, but gaseous excretion is carried out by the lungs.
Explanation:The kidneys regulate the water content of the blood by adjusting the volume of urine produced.
They help maintain blood pH and overall homeostasis by balancing acids, bases, and electrolytes.
They remove waste products such as urea and excess salts from the blood for excretion in urine.
However, carbon dioxide (
CO2) is a gaseous waste that diffuses into the lungs and is exhaled through the nostrils.
Thus, excretion of
CO2 is not a function of the kidneys — it is a function of the respiratory system.
Answer:C. Excretion of
CO2