A circulatory system is described as what?

• A. A system of tubes with a pump and valves to ensure one-way flow of blood
• B. The digestive system
• C. The nervous system
• D. The respiratory system

Answer: (A)

Think of blood traveling through a controlled loop. The circulatory system fits that description because it uses a pump (the heart) to drive blood through a network of tubes (arteries, veins, and capillaries). Valves inside the heart and some vessels keep blood moving in one direction, preventing backflow. This combination—a pump plus a system of tubes with valves to ensure one-way flow—defines how blood is circulated around the body. The other options describe different body functions: the digestive system breaks down food, the nervous system coordinates signals, and the respiratory system exchanges gases.