In that book bag, William was carrying the materials that he needed to make himself the best student in the school.

How many adverbs are in the sentence?

2?

http://www.chompchomp.com/terms.htm <~~bookmark this!

Not 2. Read about adverbs here, and let me know what you decide.

It's not 1, since that answer I put was wrong. I can still only find two. Does my BOOK bag count?

*that BOOK bag count?*

In that book bag, (prepositional phrase, used to modify "was carrying")

William (main subject)
was carrying (main verb)
materials (direct object)
that (subordinating conjunction)
he (subject of subordinate clause)
needed (verb in subordinate clause)
to make (infinitive)
himself (reflexive pronoun)
best (adjective)
student (predicate noun in subordinate clause)
in the school. (prepositional phrase, used to modify "best")

If the instructions mean one-word adverbs like shortly, quickly etc., there are none.

If the instructions mean that phrases used as adverbs can be counted, then 2 (your first answer) is correct.

Actually, there are no adverbs in the given sentence. Adverbs are words that describe verbs, adjectives, or other adverbs, and they often end in "-ly". In this sentence, the word "best" is an adjective describing the noun "student," and does not function as an adverb.