Read the sentence. In a feeding frenzy, the pigeons descended upon the breadcrumbs that the kindly old man on the park bench continued to toss.

Which is a correct analysis of the sentence?

The prepositional phrase “in a feeding frenzy” acts as a gerund phrase.
The prepositional phrase “upon the breadcrumbs” acts as a verb phrase.
The prepositional phrase “on the park bench” acts as an adjectival phrase.
The prepositional phrase “to toss” acts as an adverbial phrase.