Final answer:
The underlined phrase in the sentence is a prepositional phrase, beginning with the preposition 'with' and ending with the object 'the fruit topping', acting as an adjective.
Step-by-step explanation:
The underlined phrase in the sentence 'The cupcake with the fruit topping is yours.' is a prepositional phrase. A prepositional phrase starts with a preposition and is followed by a noun or pronoun (the object of the preposition). In this case, 'with' is the preposition and 'the fruit topping' is the object of the preposition. This prepositional phrase acts as an adjective, providing additional information about the cupcake. Prepositional phrases can also perform other functions in sentences, such as acting as adverbials. A prepositional phrase is a group of words that begins with a preposition and usually describes the relationship between two parts of a sentence. In this case, the prepositional phrase 'with the fruit topping' describes the cupcake.