What is one of the primary functions of the kidneys?

The primary function of the kidneys is to filter waste from the blood and produce urine. This process is essential for maintaining the body’s fluid and electrolyte balance. The kidneys filter out toxins, excess salts, and waste products from the bloodstream, which are then excreted as urine. This function is critical for regulating blood pressure, electrolyte levels, and overall homeostasis in the body.

In addition to waste filtration, the kidneys also play a role in regulating the volume of fluids in the body and maintaining the acid-base balance. This contributes to the body's ability to adapt to various states, such as hydration levels and metabolic needs.

The other options highlight processes that may involve the kidneys but are not their primary functions. For instance, while kidneys do produce hormones, such as erythropoietin and renin, this is not their main role. The kidneys are not responsible for regulating body temperature or absorbing nutrients from food, as these functions are carried out by different systems in the body, primarily the integumentary and digestive systems, respectively.