A structure that helps prevent food from entering the pharynx prematurely is the

Uvula

Explanation:

The uvula is that soft fleshy tissue structure that looks like the shape of a teardrop that is found at the back of your throat. It is this structure that helps in preventing food from entering the pharynx or nasal passage.

The uvula, which is made of connective tissue, saliva-producing glands and few muscle tissues, is the main structure that is responsible for all throat functions, including stopping food from entering the nasal passage by blocking the nasal passage and directing the food down your esophagus as food is swallowed.

Aside this function, the uvula also helps in fighting infections by preventing pathogens that causes disease from passing through the throat.

it creates acid rain