The best explanation for how the systems in the human body work together to maintain homeostasis and remove excess carbon dioxide during exercise is:
A. The respiratory system takes in more oxygen, and the blood transports the oxygen and carbon dioxide to and from the tissues.
This option correctly describes the role of the respiratory system in increasing oxygen intake to meet the higher demands during exercise and the role of the circulatory system in transporting oxygen to the tissues and carrying carbon dioxide away to be exhaled.