Final answer:
The epiglottis serves as a lid over the entrance of the laryngopharynx, preventing food and beverages from entering the trachea during swallowing. The correct option is A.
Step-by-step explanation:
The epiglottis acts as a lid over the entrance of the laryngopharynx. The correct answer to the student's question is a) Epiglottis. The epiglottis is a flexible piece of elastic cartilage that is attached to the thyroid cartilage and covers the opening of the trachea.
During swallowing, the epiglottis moves to a 'closed' position, resting on the glottis and effectively preventing food and beverages from entering the trachea. This function of the epiglottis is crucial as it protects the respiratory tract from aspirated food and liquids.