对垂直或车式拉紧装置，往后松动行程应在（）之间。

原先甲、乙、丙、丁四人分别坐在1、2、3、4号位子上(如图所示)。后来不停地调换位子。第一次是前后两排交换，第二次是在第一次交换后再左右两排交换，第三次再前后交换。第四次再左右交换，……。问第七十三次交换位子后，甲坐在第几号位子上（）

A．1

B．2

C．3

D．4

甲、乙、丙三人沿着400米环形跑道进行800米跑比赛，当甲跑1圈时，乙比甲多跑1/7圈，丙比甲少跑1/7圈。如果他们各自跑步的速度始终不变，那么，当乙到达终点时，甲在丙前面( )米。

A．85

B．90

C．100

D．105

阅读理解。

Hi Hongbo,

     I'm so glad to read about the changes talking place in your city. It's really good news that you can

travel by subway in Xi'an, though there's only one line there. Here in London we have twelve lines. By

the way, we don't use the word "subway" here. It's American English. We call it "the Underground",

instead.

    The London Underground is very famous. It's famous for several reasons. First of all, part of the

underground railway today is the oldest in the world, which opened in 1863. Secondly, the London

Underground is also the first line to have electric trains, in 1890. Thirdly but not the last, the London

Underground is the second largest metro system in the world, after the Shanghai Metro. There are

270 stations in the Underground and it has 402 kilometres of tracks(轨道). What's more, the city

of London itself helps make the transportation system famous! I've got a few photos to help you build

a clear picture of the Underground in my city. They are together with this mail.

     In your email, you also said workers were building more lines. I'm sure your city is developing fast.

Maybe you can send me a few photos of your city today. I really want to see the changes taking place

there. I'm happy for you to live there in an ancient city with such a new look!

So much for now. I'll write soon again. Best wishes!

1. Where is the writer from?

A. From Xi'an.    

B. From Shanghai    

C. From London    

D. From New York

2. The second paragraph mainly tells us        ?

A. when the first subway was opened in the world.

B. when the London Underground first used electric trains

C. why the London Underground is the oldest subway in the world.

D. why the London Underground is famous in the world

3. In the email, the words "subway", "underground", and "metro" mean         .

A. almost the same thing            

B. two different things

C. three different things              

D. nothing like each other

4. What does the writer want Hongbo to do? 

A. To buy a good book about Xi'an for him.

B. To post him some postcards of Xi'an.

C. To tell him more about Xi'an subway.

D. To send him a few photos of Xi'an

如设计图内没有规定或监理工程师无另有指示，试分析后张法预应力钢铰线的张拉步骤及记录内容。

家居环境铅污染主要与下列哪种家用化学品有关？（）

A.化妆品

B.洗涤剂

C.涂料

D.粘合剂

E.杀虫剂