The epiglottis seals the to prevent the bolus from entering the respiratory tract.

Trachea or windpipe

Explanation:

Epiglottis is a flap of cartilage tissue present in the throat of the human behind the tongue and in the front of the larynx or voice box. The epiglottis is present at the point where the two pipelines originate which is the trachea of the windpipe and the esophagus which brings food to the stomach.

The epiglottis can move or bend when the person swallows something and seals the trachea to prevent the entry of the swallowed substance in the respiratory organs.

Thus, Trachea or windpipe is correct.

i am going to guess that it is co2.

i'll try what topic lol