Which of these is the best analogy describing the function of the kidneys?

The kidneys regulate the body’s internal environment by filtering and processing blood. The kidney recycles minerals and resources still needed in the body while also excreting waste products. As a result, it is most like a wastewater treatment plant. The hypothalamus is the control center of the body, coordinating both endocrine and nervous system responses to information. One might consider the sites of B cell (bone marrow or lymph nodes) and T cell (thymus) maturation to be soldier training facilities in the body.