Adverbs are words that modify adjectives or verbs.
Many adverbs end in -ly, such as kindly, politely, softly, etc.
Yesterday can be either an adverb or a noun. In the way it's used here, it is an adverb.
Rachel is a name, so it is a noun, or proper noun to be precise.
worked is a verb, since it's an action. (to work)
slowly is an adverb, since it describes the verb, worked.
because is a conjunction.
she is a pronoun.
was is a verb.
so is an adverb, it describes the verb, was.
tired is an adjective.
So the answers to this question are Yesterday and so.
Hope this helps :)