In the sentence: The portrait over the fireplace was painted by my great uncle from Charleston, South Carolina. The adverbial phrase would be: over the fireplace. This is the correct answer because An adverbial phrase is two or more words that can be used as an adverb. An adverb is a word that modifies a verb, an adjective or another adverb.
Adverb phrases answer the questions: where, when, how, why. In this case the question: where? is answered: over the fireplace.
