The world itself is becoming much smaller by using modern traffic and modern communication. Life today is much easier than it was hundreds of years ago, but it has brought new problems. One of the biggest problems is pollution.
    To pollute means to make things unfit or unclean to use. Pollution comes in many ways. We see it, smell it, drink it and even eat 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 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 pollution and the development of industry(工业) have changed that. Man is slowly poisoning(毒害)not only his environment but also himself.
    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.
    The earth is our home. We must take care of it. This means keeping the land, air and water clean. And we must take care of the rise in pollution at the same time.

    Different weather makes people feel different. It influences health, intelligence (智力) and feelings.

    In August, it is very hot and wet in the southern part of the United States. People there have heart trouble and other kinds of health problems during this month. In the Northeast and the Middle West, it is very hot at some times and very cold at other times. People in these states have more heart trouble after the weather changes in February or March.

    The weather can also influence intelligence. For example, in a scientific report, IQ (智商) of a group of students was very high when a very strong wind came, but after the strong wind, their IQ was 10% below. The wind can help people have more intelligence. Very hot weather, on the other hand (另一方面), can make it lower. Students in many schools of the United States often get worse on exams in the hot months of the year (July and August).

    Weather also has a strong influence on people's feelings. Winter may be a bad time for thin people. They usually feel cold during these months. They might feel unhappy during cold weather. But fat people may have a hard time in hot summer. At about 18 ℃, people become stronger.

    Low air pressure (气压) may make people forgetful People leave more bags on buses and in shops on low-pressure days. There is a "good weather" for health. People feel best at a temperature of about I8℃.

    Are you feeling sad, tired, forgetful, or unhappy today? It may be the weather's problem.

    We all cry for water when we are thirsty. But do you know, in very hot, dry weather, plants also make very low sounds as if they are crying for help?

    You see, in a plant's stem there are several hundred "water pipes" that bring water from soil all the way up to the leaves. When the ground turns dry, it becomes harder and harder for plants to do this.

    On very hot days, plants have to get any water that they can get.

    Scientist Robot Winter has found out that when plants can get no water, their "water pipes" snap(发出声音). When that happens, the whole plant vibrates(振动) a little.

    Robot knows that healthy, well-watered plants are quiet.  He also knows that dry plants are many insects' "favourite" and they often attack(袭击) them. How do the insects know which are healthy plants and which are not? Robot thinks that the insects may hear the plants "crying" and they may come to kill them.

    When you are waiting for a bus at a station, a 31-metre-long bus is coming to you. You must be surprised. In fact, the 31-metre-long bus is the longest bus in the world. And the bus comes from Germany. An ordinary bus is only about 10 metres long and it can carry only 80 people once. But the longest bus can carry 256 people. So we will need fewer buses in the future. The longest bus can save energy, too. That's to say, it will take less energy than an ordinary bus. Moreover, the driver can drive the longest bus as easily as an ordinary one.

    However, firstly, it has to spend $ 10, 000, 000 buying the longest bus. Someone jokes that we can buy a lot of ordinary buses with that money. Secondly, people think that it is hard for the longest bus to travel on the bustling streets. It may cause new traffic problems. Thirdly, it is easy for someone to get onto the bus without buying a ticket.