12. The tiny sacs found at the end of the bronchioles. A. blood
C. alveoli
B. lymph
D spleen

Gas exchange is the delivery of oxygen from the lungs to the bloodstream, and the elimination of carbon dioxide from the bloodstream to the lungs. It occurs in the lungs between the alveoli and a network of tiny blood vessels called capillaries, which are located in the walls of the alveoli nation:

Explanation:

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