根据短文内容回答下列问题。

    It's March, 2050.

    Frank and Mary Smith wake up in their comfortable house in the morning and switch on the bedroom computer to get the latest news.

    They used to read the Times, but changed to electronic newspapers many years ago.

There is the usual news about space: another space flight has returned from Mars and scientists have discovered a new planet. Then they turn to business news: the US dollar has risen greatly in Shanghai, one of the world's leading business centers. Mary tells the computer to buy 5000 dollars, and there is a quick response that it has been done.

As they watch the screen, Mary orders one of the household robots to make coffee for them. Frank disappears into the study to join a video conference with his partners around the world. He is a computer engineer, working for several companies. This is his third job: he used to be in marketing and then television.

    Mary has a quick look at the shopping channels--the usual selection of electric cars, household robots and cheap travel offers before picking up the video phone to talk to her assistant. She also has a job and she is doing medical research. Both she and Frank used to have an office desk in London, but in 2014 they decided to move to the seaside and work from home.

    Frank and Mary have one daughter, Louise, who also has her own workstation at home. She goes to school only one day a week, mainly to play with other students. Classrooms disappeared in 2030 because there was no longer any need for them: communications systems have made it much easier to learn at home.

    Louise, now thirteen, is studying Chinese at present, which has become a world language as important as English. Louise has many Chinese friends. They communicate by computer.

    According to the family doctor, Louise will live to at least 130. Her wish is to work for a few decades(十年) and then spend her time on music and painting.

    One day, Mr. Arnold was teaching a lesson, and things were going as normally as ever. He was explaining the story of human being to his pupils. He told them that, in the beginning, men were nomads (游牧); they never stayed in the same place for very long. Instead, they would travel about, here and there, in search of food, wherever it was to be found. And when the food ran out, they would move off somewhere else.

    He taught them about the invention of farming and keeping animals. This was an important discovery, because by learning to cultivate (耕作) the land, and care for animals, mankind would always have food steadily. It also meant that people could remain living in one place, and this made it easier to set about tasks that would take a long while to finish, like building towns, cities, and all that were in them. All the children were listening attracted by this story, until Lucy jumped up:

    "And if that was so important and improved everything so much, why are we nomads all over again, Mr. Arnold?"

    Mr. Arnold didn't know what to say. Lucy was a very clever girl. He knew that she lived with her parents in a house, so she must know that her family were not nomads; so what did she mean?

    "We have all become nomads again,” continued Lucy, " The other day, outside the city, they were cutting the forest down. A while ago a fisherman told me how they fish. It's the same with everyone: when there's no more forest left, the foresters go elsewhere, and when the fish run out, the fishermen move on. That's what the nomads did, isn't it?

    The teacher nodded, thoughtfully. Really, Lucy was right. Mankind had turned into nomads. Instead of looking after the land in a way that we could be sure it would keep supplying our needs, we kept developing it until the land was bare. And then off we would go to the next place! The class spent the rest of the afternoon talking about what they could do to show how to be more civilized (文明的).

    The next day everyone attended class wearing a green T-shirt, with a message that said "I am not a nomad!"

    And, from then on, they set about showing that indeed they were not. Every time they knew they needed something, they made sure that they would get it using care and control. If they needed wood or paper, they would make sure that they got the recycled kind. They ordered their fish from fish farms, making sure that the fish they received were not too young and too small. They only used animals that were well cared for, and brought up on farms.

    And so, from their little town, those children managed to give up being nomads again, just as prehistoric men had done, so many thousands of years ago.

We've talked about snails (蜗牛) and their slow move. But much of the time snails don't move at all. They're in their shells —sleeping .

    Hot sun will dry out a snail's body. So at the least sign of hot sun, a snail draws its body into its shell and closes the opening with a thin cover. Then it goes to sleep. A snail will die in a heavy rain. So whenever it rains, it goes inside its shell house and goes to sleep. A snail can sleep for as long as it needs to. It can take a short sleep. Or it can sleep for days at a time. And it spends all the winter months in its shell, asleep.

    In spring the snail wakes up. Its body, about three inches long, comes out of from the shell. When hungry, the snail looks for food. It can't see very well. Its eyes, at the ends of the top feelers are very weak. But its sense of smell is very strong. It helps the snail to the new greens. Then the snail's little mouth goes to work.

    A snail's mouth is no longer than the point of a pin(针). Yet it has 256,000 teeth! The teeth are so small that you can't see them. But they do their work. If you put a snail in a hard paper box, it will eat its way out. And if a snail wears out its teeth, it will grow new ones.

    Mostly, a snail looks for food at night .But on cloudy days it eats in the daytime. It eats all day long. A snail can go on eating for hours and never feel full.

    In our daily life, robots are often found to do work that is too dangerous, boring, difficult, or dirty. And we often see kids play with toy robots.

    But what exactly is a robot? There are some important characteristics(特征) that a robot must have. These characteristics might help you to decide what is and what is not a robot. It will also help you to decide what you will need to build into a machine before it can be considered as a robot. A robot has these important characteristics.

    Sensing First of all, your robot would have to be able to sense the environment around it. 

    Give your robot sensors (传感器): light sensors( eyes ), touch sensors (hands), chemical sensors(nose), hearing sensors(ears) and taste sensors (tongue).

    Movement A robot needs to be able to move around its environment.  It can move on wheels, walk on legs or be driven by small engines(发动机). A robot can move either the whole body or just parts of it.

    Energy A robot needs to be able to power itself.  Some robots might power itself with sunlight, some might with electricity, while others with the battery(电池). The way your robot gets its energy will depend on what your robot needs to do.

    Intelligence A robot needs some kind of "smarts". A programmer is the person who gives the robot its "smarts". The robot will have to have a certain way to receive the program so that it knows what it is to do.

    Cars make our lives more convenient. But they can also be a problem. For example, fossil fuel(化石燃料) cars mainly cause air pollution.

    To improve the environment, many countries are developing electric vehicles(EVs，电动车). Among them, China is taking a leading role and has created the world's largest EV market.

    Last year, over 40 percent of the 753，000 EVs sold in the world were sold in China, more than twice as large as the number sold in the United States.

    "Filling up a fossil fuel car with gas(汽油) is more expensive than charging(充电) an electric car, " said Wu Hao, who bought an electric car this year.

    However, there are still some problems. It can be hard to find charging piles(充电桩) and the cars can't go far before needing to be recharged.

    Some of these problems are being solved. In 2014, China had 31，000 charging piles. Now China has the world's largest EV charging network, with more than 167，000 charging piles in total.

    Developing EVs is one of many efforts that China has made to cut down pressure on its environment after the government promised to stop increases in carbon dioxide emissions(二氧化碳排放量) by 2030.

    "As China goes, so will the world's car industry，" the Wall Street Journal said. China has taken a leading role in the world's electric vehicle industry.