Final answer:
Gas exchange in the lungs occurs in the alveoli, where oxygen is absorbed into the blood and carbon dioxide is removed.
Step-by-step explanation:
The gas exchange between the air in the lungs and the blood takes place across the walls of the c) Alveoli. The alveoli are tiny, balloon-like structures at the end of the airway branches in the lungs. Surrounded by a network of capillaries, these alveoli create a large surface area for the exchange of oxygen and carbon dioxide. When we inhale, oxygen-rich air enters the alveoli and oxygen passes into the blood, while carbon dioxide, a waste product of metabolism, moves from the blood into the alveoli to be exhaled. This process is crucial for providing oxygen to the body and removing carbon dioxide.