Here's why:
* Prepositional Phrases: These phrases start with a preposition (in this case, "on") and include an object (in this case, "top of the world").
* Function: Prepositional phrases often act as adverbs (modifying verbs, adjectives, or other adverbs) or adjectives (modifying nouns or pronouns). In this case, it acts as an adverb, describing the state of being, often meaning extremely happy or successful.
Let me know if you'd like to explore more examples or different types of phrases!