stopped. So a new network system 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, 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 very expensive and the Internet was difficult to use. By the start of the 1990s, computers had become cheaper and easier to use. Scientists had also developed software that made "surfing" the Internet more convenient.

　　Today it is easy to get online and it is said that millions of people use the Internet every day. Sending email is more and more popular among students.

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

24．The Internet has a history of around ________ years.

　　A．ten B．fifty C．twenty D．seventy

25.A new network system was set up to ________.

　　A．make itself keep on working all the time B．break down the whole network

　　C．make computers large and expensive D．make computers cheaper

26．At first the Internet was only used by ________.

　　A．Scientists B．hospitals and banks C．schools D．the government

27.________made "surfing" the Internet more convenient.

　　A．Scientists B．Software C．Information D．Computers

C

　　Animals are natural resources(资源) that people have wasted all through our history.

　　Animals have been killed for their fur and feathers(羽毛), for food, for sport, and simply because they were in the way. Thousands of kinds of animals have disappeared from the earth forever. Hundreds more are on the danger list today. About 170 kinds in the United States alone are considered in danger.

　　Why should people care? Because we need animals. And because once they are gone, there will never be any more.

　　Animals are more than just beautiful or interesting. They are more than just a source of food. Every animal has its place in the balance (平衡) of nature. Destroying one kind of animal can create many problems.

For example, when farmers killed large numbers of hawks(鹰), the farmers'stores of corn and grain were destroyed by rats and mice. Why? Because hawks eat rats and