What is the primary role of the kidneys?

The primary role of the kidneys is to filter blood and produce urine. This process is essential for maintaining homeostasis in the body. The kidneys remove waste products, excess substances, and toxins from the bloodstream, which are then excreted as urine. They also play a critical role in regulating electrolyte balance, blood pressure, and pH levels in the body by adjusting the composition of the urine. This filtration process involves nephrons, the functional units of the kidneys, which filter blood through a complex system of tubules and collecting ducts, ensuring that only the necessary substances are reabsorbed into the bloodstream while the waste is eliminated.

The other options do not reflect the primary role of the kidneys. For instance, regulating body temperature is primarily the function of the skin and circulatory system, digestion is mainly the function of the gastrointestinal tract, and oxygen delivery to the blood is the responsibility of the respiratory and circulatory systems. The unique functions of the kidneys in excretion and regulation make them vital for overall health and physiological balance.