Forests have always been useful and important to men who make use of them in many ways. Every day trees are serving man everywhere. Trees supply man with fruits and building materials in the form of wood. Without trees it would be impossible to build houses, boats, bridges and so on. Furniture such as desks, chairs and beds is made of wood. Trees can stop man from the terrible heat. They're also useful in preventing(阻止) good and rich top soil from being washed away during heavy rains. If there were no forests, heavy rains would wash away the rich surface(表层) soil that is so important to plants. The result is that the land will become a desert. There are plenty of desert areas in the world. A long time ago these desert areas used to be very rich areas, but men in the past had no enough knowledge about science of nature, and they cut down too many trees in the area where they lived and never planted new ones. By and by, the rich surface soil was blown and washed away by strong winds and heavy rains. In the end the rich land changed into useless deserts where nothing could grow.

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    Have you ever wondered how and why a fall leaf changes color? We first have to understand what leaves are and what they do.

    Plants are the world's food factories. Plants take water from the ground and take CO₂ from the air. Plants use sunlight to turn water and CO₂ into glucose(葡萄糖). Glucose is a kind of sugar. Using it as food, plants get energy and grow. Plants using sunlight to turn water and CO₂ into sugar is called photosynthesis(光合作用). ChlorophyII helps photosynthesis. It gives plants their green color.

    As summer ends and autumn comes, the days get shorter and shorter, and trees "know" to begin getting ready for winter. During winter, there is not enough light or water for photosynthesis. Trees rest during this time and live on the food they store during the summer. They begin to shut down their food — making factories. As the green chlorophyII disappears from the leaves, we begin to see yellow and orange leaves. These colors have been in the leaves all the time. We just can't see them in the summer, because they are covered up by the green chlorophyII.

    The bright reds and purples we see in leaves are made mostly in autumn. In some trees, glucose is caught in the leaves after photosynthesis stops. Sunlight and the cool nights of autumn turn this glucose into a red color. The brown color of trees is made from waste left in the leaves. It is mixture(混合物) of all these things. It makes the beautiful leaves during autumn.

    Life in the future will be different from life today.

    The population(人口) is growing fast. There will be more people in the world and most of them will live longer.

    Computer will be much smaller and more useful, and there will be at least one in each home. And computer science will be one of the most important subjects in school then. 

    People will work fewer hours than they do now, and they will have more free time for sports, watching TV and travel.

    Our food will be different, too. More land(土地) will be used for building new towns and houses for people. So there will be less land for cows and sheep, and meat will be more expensive. Maybe no one will eat it one day. They will eat more fruits and vegetables. 

    Work in the future will also be different. Robots will do dangerous and hard work. Because of this, many people will have no jobs to do. This will be a big problem in the future.  

根据短文内容，回答下列问题。

    Humans have learnt many things from nature. These things have helped us in our daily life. The latest thing is self-repairing clothing.

    Scientists have developed a special way for clothing to repair rips and tears by itself, without the need for sewing. It works with materials such as cotton, linen and wool. The scientists are from the Naval Research Office and Pennsylvania State University in the USA. Scientists Dr Walter Dressick and Dr Melik Demirel looked at how a squid can cling on to things so well. The research team found a protein in the rings of teeth that cover the suckers on a squid. The protein is similar to the one found in the silk that spiders use to make spider webs. It is very strong and elastic.

    The new protein has been developed as part of a coating, which is put on clothes. When the coating is dipped in water, the area around the rip or tear joins together in less than a minute. This could help clothes last longer and save money for us. It could also be useful for military and survival clothes. People like soldiers and mountaineers would be safer if they had clothes that could be repaired quickly and easily. Professor Demirel spoke about the invention. He said," The coatings are thin, less than a micron, so they wouldn't be noticed in everyday wear." Then he added, "Even thin, they increase the overall strength of the material. For the first time, we are making self-healing textiles."

    What is the best way to help control air pollution in our towns and cities? Choose public transportation instead of private cars, or reduce the total amount of cars on the street. These can be useful. But here is a more creative way—write a poem.

    "I write in praise of air. I was six or five, when a magician opened my fist(拳头), and I held in my hand the whole of the sky."

    Professor Tony Ryan (the science expert) and Professor Simon Armitage(the words expert), from the University of Sheffield, UK, came up with the idea.

    But in fact, the poem is not the key part. It is the poster that the poem was written on that plays the biggest part. The poster is 10 meters by 20 meters. It is coated with nanoparticles(纳米粒) of titanium dioxide (二氧化钛). It can absorb the waste from around 20 cars each day if you put it by a busy road. The poster is now displayed on one of the University of Sheffield's buildings.

    It doesn't get rid of all the pollutants from traffic, but it will eat up things called nitrogen oxides (氧化氮). These play a part in breathing problems, including asthma(哮喘).

    The technology is cheap. "It would add less than £100 to the cost of a poster and would turn advertisements into catalysts(催化剂) in more ways than one," Ryan told the BBC.

    He's also working on another idea, which is to add the nanoparticles to washing powder, so that your clothes soak up these poisons while you walk along. And you wouldn't be able to see or feel anything different.

    Mobile Apps are part of our daily life. Here are some of the most popular Apps.