Question Detail
Question
This is the actual location where the exchange of oxygen and carbon dioxide occurs in the human respiratory system.
Correct Answer
Option A is the correct answer.
Detailed Explanation
The alveoli are tiny air sacs in the lungs where gas exchange (oxygen into the blood, carbon dioxide out of the blood) takes place across their thin walls and the surrounding capillaries. The trachea, mouth, and bronchus are parts of the conducting airways, not primary sites of gas exchange.
Hint
Think about the smallest, most numerous structures at the very end of the respiratory tree.