Adverbs are the part of speech that tell us where. In the sentence, the phrase begins with a preposition and ends with the noun: schools. This makes it a prepositional phrase. The prepositional phrase is telling where Toni's father taught. Adverbs often answer the question of where the action is taking place.
The best and most correct answer among the choices provided by the question is the first choice "as an adverb prepositional phrase"
Adjective prepositional phrases<span> follow the nouns they modify, unlike adjectives which generally go immediately before the nouns they modify.</span>
I hope my answer has come to your help. God bless and have a nice day ahead!
