Answer:
Participle.
Step-by-step explanation:
It's actually a past participle, but that isn't in the answer choices.
An adverb is a word or phrase that modifies or qualifies an adjective, verb, or other adverb or a word group.
An adjective is a word or phrase naming an attribute, added to or grammatically related to a noun to modify or describe it.
So it's A.