- A Trachea
- B Bronchi
- C Alveoli
- D Diaphragm
Correct answer: C. Alveoli
Explanation: Alveoli are tiny air sacs in the lungs where O2 and CO2 are exchanged between air and blood (capillaries).
Concept context
The mechanics of breathing, lung volumes, gas transport in blood, the Bohr effect, and respiratory regulation.