Answer:
Option C, epiglottis
Explanation:
Epiglottis is a flap structure located at the larynx opening which is a separator between the upper and lower respiratory tract.
The upper part of the respiratory tract consists of Nostrils, Nasal Cavities, Pharynx, Epiglottis, and the Larynx.
After the Larynx, the upper respiratory tracts connects the trachea from where the lower respiratory tract starts. The lower respiratory tract consists of Trachea, Bronchi, Bronchioles, and the Lungs.
Hence, option C is the correct.
