The followings are the functions of the kidneys, except

The correct option is "Excretion of CO2." The kidneys are a pair of bean-shaped organs that are located in the abdomen. They are responsible for several important functions in the body, including regulation of water content, maintenance of blood pH and homeostasis, and removal of waste products from the blood. However, the excretion of CO2 is primarily carried out by the lungs through the process of respiration. The kidneys do play a role in maintaining acid-base balance in the body, but this is not related to the excretion of CO2.