The drawing of a warrior on the teepee was painted in red. a. adjective phrase b. adverb phrase

We are supposed to determine whether the prepositional phrase on the teepee is used as an adjective or adverb phrase. Even though it is telling us the location of the warrior, and should therefore be considered an adverb phrase, this is not the case here. The prepositional phrase is part of a larger, noun phrase - warrior on the teepee - and therefore it has the function of describing the noun warrior. What kind of a warrior? Warrior on the teepee.
Therefore, the correct answer is A. adjective phrase.