How do the respiratory and circulatory systems work together to maintain homeostasis?

The correct answer is: **D - By distributing oxygen throughout the body.**

The respiratory and circulatory systems work together to maintain homeostasis primarily by ensuring that oxygen is delivered to cells and tissues throughout the body and that carbon dioxide, a waste product of metabolism, is removed. The respiratory system takes in oxygen from the environment and transfers it to the blood in the lungs, while the circulatory system transports this oxygen-rich blood to the rest of the body. At the same time, the circulatory system collects carbon dioxide from the tissues and carries it back to the lungs to be exhaled, thus helping to maintain proper oxygen and carbon dioxide levels in the body.