Answer: Cilia
Explanation: Respiration can be defined as the phenomenon in which the exchange of gases takes place between the lungs and outer environment.
The process by which the air is inhaled is known as inhalation and the process y which carbon dioxide is moved out of the body is known as expiration.
The whole of the respiratory track is ciliated that protects the nasal passage by the entrance of the harmful pathogens, dirt and foreign particles. It propels out the foreign particles out of the body by the back and forth movement.