As we all know.____life is hard for any of us. If we live___ happy life,we must all work harder.
22. —Who______ it be that is knocking at the door? —It ______ be Father, but I’m not sure.
21. He apologized ________ late.
20. I got up early this morning, but I ________ so because I was not on duty today.
19. It’s dangerous to have the fire _______ at home all night long.
18. I decided to write about Chaplin, one of ______ films I had seen several years before.