Which statement best describes the function of the circulatory system?

• A. Movement of air into the lungs
• B. Movement of blood through the body
• C. Digesting and absorbing nutrients
• D. Regulating body temperature

Answer: (B)

Moving blood through the body is what the circulatory system does. This network—comprising the heart, blood, and vessels—works as a pump and highways to deliver oxygen and nutrients to every cell and to remove carbon dioxide and other wastes. That transport of blood to all tissues is the defining purpose of the system, making this statement the best description of its function.

Air movement into the lungs is the job of the respiratory system, while digestion and nutrient absorption belong to the digestive system. Regulating body temperature can be aided by blood flow, but it’s not the circulatory system’s primary function. The key idea is the continuous transport of blood to sustain cells and clear wastes.