A. need B. can C. may D. must

14. Tell me how you work out the answer, _______ you?

A. can B. will C. don’t D. shan’t

15. You promised your friend a letter; you ought to ______ days ago.

A. write B. be writing C. have written D. be written

16. She had done more work in one day than her brother _______ in three days.

A will do B. may do C. could do D. has done

17. The teacher told the student that he ______ pay for the missing magazine.

A. didn’t need to B. need not to C. mustn’t D. not had to

18. It is Saturday tomorrow. I _______ get up early.

A. don’t need B. needn’t to C. can’t D. needn’t

19. You made a lot of spelling mistakes in your composition. You ______ after you finished writing it.

A. mustn’t have gone it over B. shouldn’t have gone it over　C. needn’t have gone it over D. can’t have gone it over

20. Miss Wilson isn’t in the office, so she _______ in one of the computer rooms.

A. must work B. must be working　C. should have to work D. needs to work