16. The villagers were warned ______ the water from the river polluted by the chemical works.. 　 　A. to drink not　　　　　　 B. drinking not　　　　　 C. not to drink　　 　 　　D. not drinking　

15. Last Sunday, Ms. Green went to the Beauty Salon, ______ hairdressing and dated with Mr. Right.

A. did　　 　　 　　　 B. doing　 　　 　　　 　C. to do 　　 　　　 　　D. does

14. ______ is going to the north of Alaska to take another advantage there.

　 A. He is said that 　　　 B. It was said he 　　　 　C. It is said that he　 　 D. People said that he

13. They ______ to escape from prison last month, and now the police are still tracking them down.

A. attempted 　　 　　　 B. succeeded 　 　　　 　C. managed 　 　　　 　　D. tried

12. It was at the entrance ______ we stood chatting ______ the accident happened.

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

11. For a long time they walked without saying ______ word. Jim was the first to break _____ silence.

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

20．(本小题满分14分)

如图，已知过点的直线与椭圆交于不同的两点、，点是弦的中点．

(Ⅰ)若，求点的轨迹方程；

(Ⅱ)求的取值范围．

19．(本小题满分14分)

已知函数f(x)是定义在R上的偶函数，当

　 (1)求当x<0时，f(x)的解析式；

　 (2)试确定函数y=(x≥0)的单调区间，并证明你的结论；

　 (3)若证明：