The answers are "early, and tomorrow." Adverbs are words that makes the sentence understandable or able to be modified. Modification could include the verb, the adjective, could even be a another adverb, etc... anything that would be able to make the sentence better.
The words in the sentence that are adverbs are early and tomorrow.
Adverbs are a vast group of words that can be used to describe when, how or where an action took place. We use adverbs to give more information about a noun, a verb, an adjective or a clause. In this sentence, the words <em>early</em> and <em>tomorrow</em> are functioning as adverbs of time, telling the reader when the race starts.
