I'll be glad to check your answer.
Hint: Think of a common adverb suffix.
WRITE the adverb form that correctly completes the sentence. Hawks resemble falcons (close) of all birds.
3 answers
Is it more closely?
Yes, you have the adverb form of close. But the sentence still doesn't make much sense.
It should be
Hawks resemble falcons more closely than other birds.
It should be
Hawks resemble falcons more closely than other birds.