The adverb of a sentence is a word that defines a verb. The main verb in this sentence is the word 'includes', so we are looking for the word that defines it, makes it more specific. So let's take a look at our answer choices:
A. includes
We know that includes is the verb of the sentence, so we can nix answer A right away.
B. likely
This word describes the way in which the pictures of planes were included, so this looks like a good candidate.
C. interesting
This word is an adjective defining the pictures, not the verb of the sentence, so we can scratch it off our choices
D. many
This is another adjective defining the amount of pictures there were, so we can also remove choice D from our list.
And we're left with answer choice B.
The word 'likely' is the adverb in the sentence.
Hope that helped! =)
