Question

The exchange of gases (O${}_2$ and CO${}_2$) in humans takes place in:

• A. Trachea
• B. Bronchi
• C. Bronchiole
• D. Alveoli

Answer 1

The correct option is D Alveoli

• The oxygen in the inhaled air enters the body from the nostrils and via trachea and bronchi reaches the lungs. Inside the lungs, the bronchi branch into bronchioles. Through the bronchioles, the oxygen reaches their terminal swollen ends called the alveoli.
  
• The oxygen readily diffuses from the alveoli into the blood flowing in the nearby capillaries. The carbon dioxide from the blood moves into the alveoli and thus, exchange of oxygen and carbon dioxide occurs.
• So, the correct answer is option D.