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
（THF为一种有机溶剂）
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。
有机反应类型：___________。