The job of the human heart is to circulate blood through all of the body's arteries, capillaries, and veins. The job of the huma
n lungs is to supply the small amount of blood in them with oxygen. The interaction of these two parts of the human body results in a system that A. removes old blood from the body. B. circulates oxygen-filled blood throughout the body. C. turns the protein in blood into food energy for the digestive system. D. breaks down food energy, and turns it into heat.
