Prepositional phrases start with a preposition and other modifiers. Of the following options, the one that adds a prepositional phrase to the sentence is;
The prepositional phrase, "across the country" begins with the preposition, "across" and other modifiers.
A prepositional phrase can as an adjective in a sentence by providing further meaning to the subject being discussed.
The prepositional phrase in this instance tells us that the young artists involved in bringing social change cut across the country.
Therefore, sentence B includes a prepositional phrase.
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