28. This river has changed its course many times . It ______ always located where it _____ at present.

A. isn’t; is　　 　　　 B. isn’t; will be　　 C. wasn’t; is　　　　 D. wasn’t; has been

27. ----The Singaporean singer Stefanie Sun took the Most Popular Female Award in Hong Kong.

----But when she studied in middle school, no fans could have imagined how well she _______ in the world of entertainment.

A. would do　 　　　 B. was doing　 　　 C. had done　　 　　 D. did

26. Most children with healthy appetites are ready to eat almost anything that is offered and a child rarely dislikes food __________ it is badly cooked.

A. if　　 　　　　　 B. until　　　 　　 C. that　　 　　　　　　 D. unless

25. Generous public funding of basic science would ______ a good many benefits for the country’s health, wealth and security.

A. result from　　 B. lead to　　 　　 C. lie in　　　 　　 D. settle down

24. After the Shenzhou VI capsule(太空舱 )touched down, two astronauts succeeded in traveling around the earth, thus again __________ China is a global space power.

A. proving　　 　　 B. to prove　　 　　　　 C. to have proved　 D. being proved

23. Jim was not _______ to the club, because at that time he was not a member of it.

A. allowed　　　 　　　　 B. permitted　　　 C. admitted　　　 　 D. promoted

22. ----Did you remember to pay the telephone bill?

-----The telephone bill? ____________

A. That isn’t due yet. 　　　　 B. Are you sure?

C. My telephone is out of order. 　　　 D. Please remember the amount.

21. According to ________ announcement by Guangzhou Price Bureau, _________ new measures which have been taken recently are expected to cut the operation costs of each taxi driver by 1280 yuan

A. the; 不填　　 　　　　 B. an; the　　　　 　 C. 不填; the　　　 D. an; 不填

22.已知双曲线C的中心在原点，抛物线的焦点F是双曲线C的一个焦点，且双曲线过点，过焦点F且斜率方向向量＝(－2，1)的直线与双曲线的左、右两支分别交于点， 　 　　　　　　　

(1)求双曲线的方程；(2)求证：为定值；(3)求的值

21．已知，若时恒成立，求的取值范围.