Two friends are eating together on a dining table. One of them suddenly starts coughing while swallowing some food. This coughing would have been due to improper movement of:

The epiglottis is a cartilaginous flap that covers the glottis (opening of the windpipe) during swallowing to prevent food from entering the respiratory tract. Improper movement can cause food to enter the trachea, triggering a cough reflex.