How is the circulatory system involved with the respiratory system?
A. It moves air into the lungs.
B. It moves red blood cells to the larynx so sounds can be made.
C. Oxygen and carbon dioxide diffuse in and out of the capillaries that surround alveoli.
D. Blood pressure keeps the C-shaped rings in the trachea from collapsing.

A. It moves air into the lungs.

Explanation:  The respiratory system works directly with the circulatory system to provide oxygen to the body. Oxygen taken in from the respiratory system moves into blood vessels that then circulate oxygen-rich blood to tissues and cells.

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