HELP ME OUT PLEASE!!!

Which answer choice best explains how the bolded participial phrase is used in this sentence?

The elderly couple dancing the tango in the ballroom swayed to the rhythms of the song.

O It is used as the subject noun of the sentence.

O It is the active verb in the sentence.

O It is an adverb modifying the verb swayed.

O It is an adjective to describe the word couple.​