3. Every means ______ (be) tried but without much result.

6. Not only I but also David and Iris ______ (be ) fond of playing basketball.

11. Three hours ______ (be) enough for us to finish the task.

13. All that can be done ______(do).

14. One or perhaps more pages _______(miss).

19. Cattle ______ (eat) grass on the hillside.

21. Mary is one of the girls who ______ (be )always on time.

27. No one except two students ______ (be late for) the meeting yesterday.

29. Interest, as well as prospects, ______(be ) important when one looks for a

30. A number of cars ______(park) in front of the park.

学习反思