25、Small sailboats can easily turn over in the water ________.

A. if not managed carefully                                 B. if are not managed carefully

C. unless not managed carefully                           D. unless are not managed carefully

24、---It seems that he has succeeded in this year’s entrance examination to the college.

---Yes, but you can not imagine ______ during the past three years.

A. what a hard life he has experienced                  B. what he has experienced a hard life

C. he has experienced what a hard life                  D. what a hard life has he experienced

23、 _______ environmental damage is done, it takes many years for the ecosystem to recover.

A. Even if                       B. If only                      C. While                       D. Once

22、Jack is said _____ abroad for three years, but I didn’t know about it.

A. studying                     B. to have studied          C. having studied           D. to study

21、Was it when you were talking with a friend under the tree ______ your bike was gone?

A. that                           B. where                      C. which                      D. while

20、Nobody knows the exact number of people and cattle _____ were drowned in the flood.

       A. which                      B. who                         C. whom                      D. that

19、The young couple ______ to take a walk after dinner every evening.

   A. make it a rule              B. make that a rule         C. make a rule               D. make those rules

18、Teachers always remind us of some reading skills _____ we should pay attention.

A. about which               B. to which                   C. with which               D. on which

17、 _____ from the fifth floor when the policemen surrounded him.

A. Jumped down the thief                                          B. Down the thief jumped

C. Down jumped the thief                                          D. Down did the thief jump

16、The year 2008 ______ the most splendid Olympic Games in human history in Beijing.

A. has witnessed             B. witnessed                 C. had witnessed           D. have witnessed