It's very important _______ us ______ every day.
--Have you got _______ ready for the school trip? ---Not yet. We still have _______ to do.
---Jack, _______ have you been away from your hometown?---Since the end of last February.
How can you study in the living room when other people are watching TV? I think you need a _______ place.
--- Mr. Green, I think physics is too difficult for me. ---Tom, work hard, _______ you’ll find it not as difficult.
--- Listen! David is talking happily with his mother in the next room. --- It ______ be his mother. She has gone to Yunnan to be a volunteer doctor.