Matelita found her favorite hat behind the living room couch, which excited her greatly.

what accurately describes the underlined portion of the sentence?

adverbial clause
adjectival clause
appositive phrase
prepositional phrase

An adjective clause is simply a group of words with a subject and a verb that provide a description. The clause starts with a pronoun such as who, whom, that, or which or an adverb such as when, where and why. but i think is the second one adjectival clause. 

So, what’s the question here?

Ithink the answer will be a