Which sentence uses a prepositional phrase?

O My dog barks really loudly
O We like to go running
O The food fell under the table
O I am going to eat dinner later

The food fell under the table.

Is this %100 percent correct?

Yes, the sentence "The food fell under the table" uses a prepositional phrase. The word "under" is a preposition, and "the table" is the object of the preposition.