The cartilage in the throat that guards the entrance to the trachea and prevents fluid and food from entering it when a person swallows is known as the

The epiglottis

The cartilage in the throat that guards the entrance to the trachea and prevents fluid and food from entering it when a person swallows is known as the epiglottis .

The epiglottis is an elastic flap located at the upper end of the larynx in the throat. The epiglottis is the valve that turns passage to either the esophagus or the trachea. The epiglottis allows air to enter the airway to the lungs during breathing, and during swallowing, it allows food and fluids to pass into the gastrointestinal tract.  

the correct answer, according to e2020, is the second choice there is an occluded front in region a and a cold front in region b.