5. I got caught in the rain and my suit____.

A. has ruined 　　　　　 B. had ruined　 　　　　　　 C. has been ruined　 D. had been ruined

4. Mom, have a rest please. You 　_______ in the kitchen ever since you came home.

A. had worked 　　　　 B. were working 　　　　　 C. have been working　 　　 D. would work

3. My mind wasn’t on what he 　so I’m afraid I missed half of it.

A. was saying 　　　　　 B. had said　 　　　　　　　　 C. would say　 　　　　 D. has said

2.-Let Mr. Stephen in, please? He 　　　　 　me.

-Yes, Sir. In the meeting room.

A. is expecting　　　　　 B. has expected　 　　 C. expected　 　　　 D. was expecting

1. -I am wondering if we could go boating on the weekend.

-It 　　　a good idea.

A. sound　　　　　　　　　　　 B. sounded 　　　　　　　　　　 C. sounding 　　　　　　　　 D. sounds

25. (本大题8分)已知等差数列的前n项的和为,且公差,

(1).求数列的通项公式

(2).从数列中依次取出求数列的前n项和

24. (本大题8分)现有一批货物由海上从A地运往B地,已知货船的最大航行速度为50海里/小时,A地到B地的航行距离为500海里,每小时的运输成本由燃料费和其余费用组成,货船每小时的燃料费用与货船速度的平方成正比(比例系数为0.6),其余费用为每小时960元.

(1)把全程运输成本y(元)表示为货速度x(海里/小时)的函数

(2)为了使全程运输成本最低,货船应以多大速度行驶?

23.(本大题8分)已知函数

(1)若的最大值为1,求的值

(2)当时,恒成立,求实数的取值范围

21.(本大题8分)已知,且的夹角为120⁰

(1)　 若,求的值

(2)　 求的值

22 (本大题8分)某商场为了调查旅游鞋的销售情况,随机抽取了40位顾客的购鞋尺寸,将所得数据整理后,画出频率分布直方图如下,其中直方图从左到右前3个小矩形的面积之比为,试估计

(1)　　 购鞋尺寸在39.5-43.5内的顾客所占的百分比是多少?

(2)　　 样本数据的中位数是多少?(精确到0.01)

20.在△ABC中,AB=3, AC=2,D是BC的中点,则______

三:解答题(本大题共40分)