Final answer:
Gas exchange takes place in the respiratory division of the lower respiratory tract (option D), specifically in the alveoli of the lungs.
Step-by-step explanation:
Gas exchange occurs in the respiratory division of the lower respiratory tract. The lower respiratory tract includes the trachea, bronchi, bronchioles, and the lungs, but it is only in the lungs where the gas exchange actually takes place. The crucial components involved in gas exchange are the alveoli, small air sacs where oxygen and carbon dioxide are exchanged between the air and the blood in the surrounding capillaries. Therefore, the correct answer to the student's question is D. Respiratory division of the lower respiratory tract.