Where does the actual gas exchange happen? a. alveoli
b. bronchi
c. bronchioles
d. cilia

Option a. is correct.

Explanation:

Gas exchange refers to the the elimination of carbon dioxide from the bloodstream to the lungs and delivery of oxygen from the lungs to the bloodstream. The actual gas exchange happens in the lungs between the alveoli and capillaries (a network of tiny blood vessels). Capillaries are located in the walls of the alveoli.

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