17、 I just don't understand _________ that prevents so many Americans from being as happy as one might expect.

    A. why it does        B. what it does       C. what it is          D. why it is

16、 The theory he's stuck _____________ us that earthquake can be forecast.

    A. to proves          B. to prove           C. to proving          D. to proved

15、--May I go and play with Tom this afternoon, Mum?

--No. You can't go out _____________ your homework is being done.

    A. before             B. as                  C. until               D. after

14、--Remember the first time we met, Jim?

-- Of course I do. You _____________ in the library.

    A. had read           B. were reading       C. have read          D. read

13、If you want to see a doctor, you fix a date with him ahead of time. That is a common __________ in the USA.

    A. sense              B. rule                C. practice            D. reality

12、 This crop does not do well in soils _____________ the one for which it has been specially developed.

    A. outside            B. other than         C. beyond            D. rather than

11、I won't think _____________ of him because of his shortcomings. He is a good boy after all.

    A. much              B. little               C. any less            D. any more

10、____________ is known to the world is ___________ Mark Twain is a great American writer.

    A. It, that           B. What,  /             C. As,  /              D. What, that

9、So difficult _____________ it to live in an English speaking country that I determined to learn English well.

    A. I have felt         B. have I felt         C. I did feel          D. did I feel

8、I do feel _____________ Chinese language is _____________ most difficult one.

    A. a; the             B. the; a             C. /; a               D. the; /