Question

what tube acts as the trunk of the respiratory tree?
pharynx
larynx
trachea
main bronchus

Explanation:

The trachea is often considered the trunk of the respiratory tree. It is a large - diameter tube that branches into the main bronchi. The pharynx and larynx are upper respiratory structures but not the trunk of the respiratory tree. The main bronchi are branches from the trachea.

Answer:

Trachea