This chapter is so difficult to ______ that I shall have to read it again later.
After the long journey, the Smiths returned home, ____.
Not everyone has realized what_______ important part the balance of________ nature plays in their life.
It’s easier to catch a _____ lion than the one that’s awake.
Mr. Smith didn’t go to the party because he had a lot of experiments _____.
Only if he gets a job ______ have enough money to build his own house.