What is the function of the kidneys?

The function of the kidneys, which is correctly identified in the answer, primarily involves filtering waste products from the bloodstream and producing urine. This critical process helps maintain the body's chemical balance and eliminate excess substances, such as salts and toxins. The kidneys regulate various bodily functions, including fluid balance, electrolyte levels, and blood pressure. They also play a role in the production of hormones that influence red blood cell production and calcium metabolism. However, the primary and defining function of the kidneys remains their ability to filter blood, remove waste, and produce urine, thus ensuring that the body can efficiently manage and dispose of waste materials.