在累进税率的分类中，使用时间较长和应用较多的是( )。A．全额累进税率 B．超额累

水泵、水箱和消防设备对业主或使用人日常生活、生命财产安全关系重大，你知道该怎样加强日常性保养吗？

The Migration of Birds

Here is a scientific experiment on the homing of birds, the fact of which are quite certain. A few years ago seven swallows were caught near their nests at Bremen in Germany. They were marked with a red dye on some of their white feathers, so that they could easily been seen. Then they were taken by plane to Croydon, near London. This is a distance of 400 miles.

Then the seven swallows were set free at Croydon. Five of them flew back to their nests at Bremen. How did the birds find their way on that long journey, which they had never made before? That is the great puzzle. It is no good saying that the swallows have a sense of direction. These are just words and explain nothing. We want to know exactly what senses the animals use to find their way, how they know in which direction to go until they can see familiar landmarks. Unfortunately practically no scientific experiments have yet been made on this question.

Perhaps migrating birds are the greatest mystery of all. Swallows leave England in August and September, and they fly to Africa, where they stay during our winter. The swallows return to England in the late summer for the south. A lot has been found about the journeys of migrating birds by marking the birds with aluminum rings put on one leg. An address and a number is put on the ring.

Swallows from England go as far as South Africa and as many as fourteen birds, marked with rings in England, have been caught again in South Africa. From England to South Africa is a journey of 6,000 miles. And the birds not only return from Africa to England next spring, but often they come back to the nests in the very same house where they nested the year before.

17．The seven swallows were marked on some of their feathers because       .

A．they would be taken away by plane

B．they would be free in London

C．Croydon was 400 miles away

D．they could easily be seen for the red colour

18．Which of the following is true?       .

A．Seientists have found why the animals can see their nests.

B．No one knows why the swallows can fly back to their familiar landmarks.

C．It’s very simple that the birds use sense of direction.

D．Many experiments have been made on how birds can fly their way home

19．Swallows like to spend ”our winter” in        .

A．England      B．London        C．Africa       D．Germany

20．When do the birds return from South Africa to England every year?

A．summer        B．spring        C．winter         D．Both A and B

开放性作文。     

      如今世界粮食短缺，价格飞涨，给部分地区造成社会动荡．假设在你校开展的研究性学习中，你们小组以“World Food Crisis”为题进行研究，现在请你代表你们小组向全体同学简要介绍你们的研究成果．主要内容（三个部分）如下：     

     1．造成的原因：     

     1)气候变化，造成粮食减产     

     2)工业发展，城市化加速，耕地减少     

     3)世界能源价格上涨，使用粮食生产生物燃料     

     2．应对的措施：（第一点已经给出，第二点自己写）     

     1)注重环保，改善生态     

     2)……     

     3)我们学生需要做什么（自己自由发挥）

注意：     

    包括以上要点，但不要逐句翻译     字数120左右，文章开头已提供，不计人总词数     

    参考词汇：城市化urbanization；生物燃料biofuels       

Good Moming/Aftemoon/Evening folks,     

    It's my pleasure to be here today representing my group, to report a research project“The World 

Food Crisis". As you might know, food shortages have hit many countries across the world and even 

caused many social problems in lots of areas.  But who is responsible for the current world food crisis? 

There are a couple of fundamental factors behind this. 

     _____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

轻骨料混凝土的弹性模量与普通混凝土相比（）。

A．高10%～20%

B．低10%～20%

C．高20%～50%

D．高20%～50%

教学活动的构成有（）。

A.上课

B.作业

C.辅导

D.成绩评定

E.社会实践