27. ― The light in the office is still on.

     ― Oh , I forgot            .

     A.  turning it off   B. turn it off    C. to turn it off   D. having turned it off

26. Tom's mother kept telling him that he should work harder , but          didn't help .

    A. he          B. which           C. she        D. it

25. I don't know what was             for supper .

     A. it         B. there          C. that            D. food

24. She is already 50 , but she doesn't look                .

     A. like             B. this            C. it D. such

23. It is not you who               in trouble ; it is I who             in trouble .

     A. are ; am      B. are ; is       C. are ; are     D. is ; is

22. We think           useless            theory without practice .

     A. it ; learning B. it ; learn     C. that ; learning           D. that ; to learn

21. My pen is lost and I can't find           anywhere , so I must buy            .

     A. it ; one B. one ; it            C. it ; it          D. one ; one

20. I find             difficult               him to do such work .

     A. it ; of          B. it ; for        C. that ; of             D. that ; for

19. Look , someone is coming . Who can              be ?

     A. he B. she           C. that man            D. it

18.            is no doubt that he will succeed in his experiment .

     A. It         B. This           C. That           D. There