Question

which is a principal structure of the ventilatory system capillary trachea pulmonary valve pulmonary artery

Explanation:

The trachea is a main airway in the ventilatory (respiratory) system, transporting air to and from the lungs. Capillaries are part of the circulatory - gas - exchange system but not a principal ventilatory structure. Pulmonary valves are related to the heart's blood - flow in the pulmonary circuit and pulmonary arteries carry de - oxygenated blood to the lungs, which are more related to the circulatory system in the context of lung function rather than being principal ventilatory structures.

Answer:

B. trachea