Answer:
The correct answer is alveoli or alveoli sac.
Explanation:
Alveoli are an essential part of the respiratory system present in lungs whose role is to exchange carbon dioxide and time molecules to the blood and from the bloodstream.
These balloon-like tiny air sacs present at the end of the respiratory tree. These are arranged in clusters in the lungs.
Thus, the correct answer would be the alveoli or alveoli sac.
