People have lots of problems living in the central Australian desert, ____ the lack of water is the most serious one.

Listen! Someone is knocking at the door. Who _____it be?—It _____be Tom. He phoned to visit me this evening.

I suppose you are at least 60 years old.- Thank you. I’m glad you______ that. My real age is 362.

All of us found ________ hard to get along with him, he was too strict with others but not with himself.

Another cup of coffee? —No. thanks. I _____ be off. Marry is waiting for me.