Question

where does gas exchange occur in our lungs?
trachea
alveolar sacs
bronchioles
bronchi

Explanation:

Gas exchange in the lungs occurs in the alveolar sacs. The trachea is the windpipe, bronchi are the main airways into the lungs, and bronchioles are smaller airways. Alveolar sacs have thin walls and a large surface area, which is ideal for the diffusion of oxygen and carbon dioxide between the air and the blood.

Answer:

alveolar sacs