Question

Determine the use of the prepositional phrase in the following sentence.

The basketball on the roof is Jerod's.


adjective

adverb

Answer 1

We are given the sentence,  "The basketball on the roof is Jerod's". THe prepositional phrase is "on the roof". The phrase describes the basketball which is a noun. A word or group of words that describes a noun is called an adjective. 

Answer 2

The use of the prepositional phrase in this sentence is adjective, because it is part of the noun phrase - the basketball on the roof.
If it weren't a part of the phrase, it would probably be an adverb, but this way, it is not.