The correct answer is nephrons. The kidneys contain millions of tiny filtering units called nephrons. These nephrons are responsible for filtering waste products and excess water from the blood to produce urine. To find the answer to this question, you can use various methods. One way is to consult a reliable source such as a textbook or website that provides information about the structure and function of the kidneys. Another way is to use a search engine and enter the keywords "kidney filtering units." This should lead you to sources that explain the concept of nephrons in more detail and confirm that nephrons are indeed the correct answer to the question.
