E

    The Earth is our home; we must take care of it. This means keeping the land, air and water clean. Pollution is a dirty word. To pollute means to make things unfit or unclean to use. Pollution comes in many ways. We see it, smell it, taste it and drink it. Pollution is beginning to threaten (威胁) our health, our happiness and our life. Man has been polluting the earth from the time he first made fire, washed his clothes in the river and threw his waste on the ground. When land was used up or water became dirty, men moved on to another place. At first, the problem was not so serious because there was plenty of clean air, land and water. There weren't so many people then and their wants were fewer. All the dirty things could be absorbed (吸收) by nature and soon covered over. But this is no longer true. The increase of population and the development of industry(工业)have changed that. Man is slowly poisoning (毒害) his environment. Through the use of poison, man has polluted the land, killing the animals. By putting dirty water and chemicals into rivers and lakes we have polluted our drinking water, killing the fish.

    Our increasing population is part of the problem. More people, more waste.

    Where is this all to end? Are we turning the world into a big rubbish dump (堆存处), or is there any hope that we can get rid of (摆脱, 除去) the pollution? Luckily, millions of people have been warned of the danger of pollution. Large numbers of people are now working hard to bring pollution under control.

    As space science develops, man has learnt more and more about space. Space is not only amazing but also dangerous. While working in space, spacemen are facing danger as well as success.

    Scientists have found out that the radiation is the greatest danger to spacemen in space. When spacemen are working in space, they are in danger of the radiation from the Sun and other stars, which is bad for their health.

    Space rubbish is also a great danger to spacemen. It's reported that there were 9,000 man-made things flying in space. About 30% of these are satellites, 10% are spaceships, and the rest space rubbish. A small piece of these can knock a spaceship window and cause some damage.

    Scientists are watching and reporting any possible danger all the time. They are working to deal with space rubbish. Although space is really dangerous, it interests many people on Earth. In the near future, it may become possible for people to spend a few days in a space hotel. We may even choose to leave the Earth and live in space in a few years. So we should do something to help improve the space environment.

A robot could understand your words and follow your instructions(指令) to do things. There're many kinds of robots. Each kind of robot has a different job. 

There are waiter robots. They can clean the table and serve the dishes. Household(家庭) robots do many things at home. They lift furniture, clean the room and even do some cooking. Sales robots work as salesmen. They can sell flowers, newspapers, and many other things. Recently, a Japanese company has showed a guard dog robot. It keeps the pet dog at home. And a company puts its singing and dancing robots on show. The robots are not for sale. 

In the future, we will have more robots. They will be a great help to our life. Maybe you can walk with your robot dog on the street. How interesting it will be!

Do you know your mobile phone number well? You may sometimes find it hard to remember your number. That's because China has the longest mobile phone numbers in the world. Why is that? 

The 11 digits (数字) include three parts. Each part has a different meaning. The first three numbers tell you the mobile phone service provider (服务提供商) you are using. For example, 135 is for the China Mobile Communication Corporation (中国移动) and 186 is for China Unicorn (中国联通). The fourth to the seventh digits tell you where the number is from. And the last four digits are random (随机的). 

The main reason for using 11 digits is that we have the largest population (人口) in the world. We once had 10 numbers. But as our population grew, there were not enough numbers for us to use. So we began to use 11 digits from 1999. 

11 digits can make tens of billions of mobile phone numbers. That's enough for each person to have seven or eight phone numbers to use in China. Also, we can reuse the mobile phone numbers. Usually, the service provider will use a canceled number again after three to six months. If you call a number that you haven't called for a long time, you may find its owner has changed. 

Besides China, Britain and Japan also use 11-digit mobile phone numbers. But their numbers always start with 0. So they cannot make as many numbers as we can. Countries like the United States, Australia and India use phone numbers with 10 digits. Canada's mobile phone numbers are perhaps the world's shortest: they use seven digits.