The larynx is just the tube at the top of the respiratory tract, so it cannot close itself. The trachea is the cartilaginous portion of respiratory tract below the larynx so it cannot close the top of the larynx. The esophagus is what the larynx separates from and connects the buccal cavity (mouth) to the stomach, so it cannot close the larynx. The epiglottis is a cartilaginous plate at the top of the larynx that closes the larynx when you swallow so fluids and food stuff does not go into the lungs and opens to breathe after the end of the swallow. The answer would be the epiglottis.
