5.　 to receive

4.　 weren’t listening

3.　 are sweeping

2.　 using

1.　 have taught

28. She doesn't know what_________ (do) and where__________ (go).

27. Would please tell us how___________ (make) the watch ________ (work)?

26. The radio__________ (use) once in a week in our class. 　It____________ (not use) yesterday because there was something wrong with it.

25. The old man often_________ (tell) the children a story in the evening. This evening he ________ (tell) two stories.

24. They find it useful__________ (learn) English.