500kV电压互感器出厂验收，绝缘油击穿电压应（）。 A.大于等于70kV B.大于

阅读理解。

     We are all busy talking about and using the Internet, but how many of us know about the history of

the Internet?

     Many people are surprised when they find that the Internet was set up in the 1960s. At that time,

computers were large and expensive. Computer networks (网络) didn't work well. If one computer in the network broke down, then the whole network stopped. So a new network system (系统) had to be set

up. It should be good enough to be used by many different computers. If part of the network was not

working, information could be sent through another part. In this way the computer network system would keep on working all the time.

     At first, the Internet was only used by the government, but in the early 1970s, universities, hospitals

and banks were allowed to use it too. However, computers were still expensive and the Internet was

difficult to use. By the start of the 1990s, computers become cheaper and easier to use. Scientists had

also developed software (软件) that made "surfing (浏览)" the Internet more convenient (方便).

     Today it is easy to get on-line and it is said that millions of people use the Internet every day. Sending e-mail is more and more popular among students.

     The Internet has now become one of the most important parts of people's life.

1. The Internet has a history of ________ years.

A. about 40           

B. less than 30

C. more than 45      

D. nearly 35

2. Scientists set up a new network system to ________.

A. make the computer cheaper    

B. make the system work well

C. make the computer go well    

D. develop new softwares

3. The Internet was widely used in the ________.

A. 1960s  

B. 1970s    

C. 1980s    

D. 1990s

4. The underlined words "get on-line" in Chinese mean ________.

A. 上机    

B. 上网

C. 接线    

D. 买电脑

把一元二次方程（x-5）²=36化为一般形式是______．

某工厂生产酒精，要求含水量（按质量计算）不超过10%，他们用抽测密度的方法对产品进行检查，则合格酒精的密度应在______kg/m³至______kg/m³范围内（不考虑酒精与水混合后的体积变化）．

15分）有机物A、D均是重要的有机合成中间体，D被称为佳味醇（chavicol），具有特殊芳香的液体，也可直接作农药使用。下图所示的是由苯酚为原料合成A、D的流程。

已知：

①  （THF为一种有机溶剂）

②

③请回答下列问题：

（1）写出A、C、D的结构简式___________、_____________、_______________。

（2）是化合物B的一种同分异构体，用¹H核磁共振谱可以证明该化合物中有______种氢处于不同的化学环境。

（3）指出有机反应类型：___________。

（4）化合物B经过下列转化，可合成用于制造树脂、合成橡胶乳液的有机原料丙烯酸。

①设置反应②、⑥的目的是______________________。

②写出反应③的化学反应方程式 ___________________________。

③G与甲醇反应生成的酯H是生产丙烯酸树脂的一种重要单体，写出H聚合的化学反应方程式_____________________________。

不属于光电电子战对抗领域的是（）。

A.激光对抗

B.红外对抗

C.光电电子防御

D.可见光对抗