Which sentence is correct?

Question

She handed the hard working teacher the all important test.
She handed the hardworking teacher the allimportant test.
She handed the hard-working teacher the all-important test.

Answer 1

The correct sentence is:

She handed the hard-working teacher the all-important test.

In this sentence, "hard-working" and "all-important" are correctly hyphenated because they are compound adjectives that describe a noun.