I am having a difficult time identifying whether the prepositional phrase in the following sentence is acting as an adverb or an adjective. Here is the sentence:
Did they really buy all the guys tickets for the birthday party?
It seems to me that the prepositional phrase "for the birthday party" is functioning as an adjective, as it is describing the tickets. Which tickets? The tickets for the birthday party. However, my grammar book—which contains this sentence as an example—states that the phrase is modifying "buy."
Is this because the prepositional phrase is adding more context to why the subject bought the tickets?