Answer: Mucosa: sub mucosa : adventitia
Step-by-step explanation:
Respiratory tract is a part of respiratory system that helps in the process of respiration.
The respiratory tract is lined with different layers of wall. Moving from the inside to outside of the respiratory tract the layers are mucosa; sub mucosa and the outermost wall is adventitia.
These layers helps in protecting the respiratory system from any kind of damage and kills the harmful pathogen that tries to enter the tract.