What is the role of the kidneys in the body?

The role of the kidneys in the body primarily focuses on filtering blood and excreting waste products. The kidneys are vital organs that perform essential functions to maintain homeostasis. They filter out toxins, excess salts, and waste products such as urea from the bloodstream, which are then excreted in the urine. This process helps to regulate the composition of the blood, ensuring that electrolyte levels and acid-base balance remain within a healthy range.

Additionally, kidneys play a significant role in regulating blood pressure, fluid balance, and the formation of red blood cells through the production of erythropoietin, a hormone that stimulates red blood cell production in the bone marrow. They also help in maintaining the body's pH balance by selectively reabsorbing bicarbonate and secreting hydrogen ions.

In contrast, other choices do not accurately describe the function of the kidneys. Bile production is a function of the liver, blood sugar regulation is primarily managed by the pancreas, and nutrient absorption occurs mainly in the intestines. These distinctions highlight the unique and crucial role of the kidneys in excretory and regulatory processes within the body.