Final answer:
The two major zones of the respiratory system are the conducting zone and the respiratory zone, which are responsible for filtering air and gas exchange, respectively.
Step-by-step explanation:
The respiratory system can be functionally divided into two major zones: the conducting zone and the respiratory zone. The conducting zone includes all the pathways that air travels through to reach the lungs, like the nasal cavity, pharynx, trachea, bronchi, and bronchioles. This zone has the crucial role of filtering, warming, and humidifying the air we breathe in.
In contrast, the respiratory zone is directly involved in gas exchange with the blood. It begins at the terminal bronchioles, continues through the respiratory bronchioles, and then leads to the alveolar ducts which open into the clusters of alveoli. Here, oxygen enters the blood and carbon dioxide is removed, which is the primary function of the respiratory system.
Therefore, the correct answer to the question is D) conducting and respiratory, which are the two main functional zones of the respiratory system.