Final answer:
The prepositional phrase 'At the carnival' serves as an adverbial phrase, modifying the verb 'won' in the sentence. It adds detail by telling us where Rip Hunter won a goldfish.
Step-by-step explanation:
In the sentence 'At the carnival, Rip Hunter won a goldfish,' the prepositional phrase is 'At the carnival'. This adverbial phrase modifies the verb 'won' as it provides context to where the action of winning took place.
Prepositional phrases can function as adjectives or adverbs. When functioning as adverbs, they often provide information about where, when, or how the action of the verb is being performed.
In English grammar, prepositional phrases typically consist of a preposition followed by a noun or pronoun that serves as the object of the preposition. The entire phrase then acts together to modify another word in the sentence, which is the complete thought here.