Gas exchange in mammalian lungs occurs in the ____.

A) villi
B) anterior air sacs
C) posterior air sacs
D) bronchioles
E) alveoli

Alveoli

Tiny air sacs in the lungs where the exchange of oxygen and carbon dioxide takes place.

Bronchioles

The small passages in the lungs that lead air to and from the alveoli, instrumental in the process of breathing.

Gas Exchange

The biological process through which organisms exchange oxygen and carbon dioxide with their environment, fundamental in respiration and photosynthesis.