The correct answer is C. Verb
Explanation:
You can identify a prepositional phrase because it includes a preposition such as under, with, besides, by, etc. and an object related to it (object of the preposition). Also, depending on their location in the sentence and content they can modify or describe a noun, pronoun, or verb.
In the case of the sentence presented, the sections "down to the river" and "before His cousin" are both prepositional phrases because they contain the prepositions "down" and "before", also, these two prepositional phrases modify the words "went" and "stood"; this means the words modify by the prepositional phrases are actions or verbs.
