29.　 - Has the plane arrived?　 - Yes. It _______ (arrive) five minutes ago.

28.　 Our classroom is so clean. Who __________ (clean) it?

27.　 - Shall we go for a walk?

- I’d love to, but I ________ (not finish) my homework.

26.　 It’s a long time since we ________ (meet) last time.

25.　 We should send the child to hospital. He ________ (not eat) anything for two days.

24.　 Mike knows the Great Wall well because he_______ (be) there many times.

23.　 We often see some students _______ (pick) up some rubbish and _______ (throw)

it into a dustbin. What good students!

22.　 Whenever someone ______ (throw) in some rubbish, it produces a piece of music.

21.　 I can’t open the door. I _________ (lose) my key.

20.　 I don’t think Sam can help you now, because he ______ (go) to the supermarket.