What is the function of the kidney?

• A. It stores urine.
• B. It regulates blood sugar.
• C. It filters toxins from the air.
• D. It removes waste from the blood.

Answer: (D)

Think of the kidneys as the body's filtration and balance system. Their main job is to filter waste products from the blood and regulate the volume and composition of body fluids, including salts and acids. This means they remove waste from the blood, produce urine, and help keep the body's chemical balance in check. Urine is stored in the bladder, not the kidneys. Regulating blood sugar isn’t a primary kidney function—that role belongs to the pancreas and liver. The lungs handle filtering toxins from the air. So, removing waste from the blood best describes the kidney’s function.