Either you must stop eating my food from the refrigerator or you must pay me for it.
what is a prepositional phrase in the sentence?
a. from the refrigerator b. must stop c. pay me d. eating my food

The prepositional phrase in the sentence "Either you must stop eating my food from the refrigerator or you must pay me for it." is  A. "from the refrigerator"

A prepositional phrase is a phrase that consists of a preposition and an object which is linked to the object. A preposition is a word that usually governs or precedes a noun. An object is a noun that comes after the subject and the verb. A simple example of a sentence that includes a subject, verb and object is:
The cat sat on the mat.
"The cat" is the subject."sat" is the verb and the prepositional phrase that includes the object is "on the mat" 

The last one is right