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    For many years, scientists have said that the earth is getting warmer. Now they have found something new—hot cities! In the southern US, they have found that cities become very hot in summer. For example, the city of Atlanta in Georgia has roof(屋顶) temperature of up to 50^oC while it is 27℃ in the streets! At night, the outside of buildings stays so hot that the heat of the city causes storms over the city!

    China also has the same kind of problems. Every year more farmland is used for factories or offices. More housing is needed, too. As people become richer, they buy more cars. New roads are needed and new car parks are built in the city centers. This all makes cities hotter.

    It isn't easy to change the situation. City planners say that we should plant more trees in the middle of cities. Every new street should have trees on both sides, they say. Trees make the temperature lower, so we should have more trees in our parks and squares. We should also paint our roofs white. If we do this, they do not become so hot. Every roof in a hot and sunny country should have solar(太阳的) roof panels. The electricity from these can be used to run the air conditioners (空调)in the buildings.

    People continue to cut down forests around the cities. This makes the problem worse. Cities are growing faster and faster. By the year 2025, four fifths(五分之四) of the population will be living in cities. If we go on like this, there will not be enough farmland to feed everyone in the world.

    ①What does the city of the future look like? Flying cars? Robots? Or smog（烟雾）-eating buildings?

    ②Arconic, an American company, has made plans to build a 4.8-kilometer-high skyscraper（摩天大楼）. It says that the super tall building can clean not only itself but also the air around it by “eating” smog and pollutants（污染物）. But how is it done?

    ③Sherri McCleary, s scientist at Arconic, says they have introduced a new technology called EcoClean. It is a special coating that pulls pollutants out of the air. With a little help from sunlight and water vapour（水蒸气），the coating will produce atoms（原子能）called free radicals（自由基）. It is these free radicals that will take in air pollutants, break them down, and then leave the air cleaner.

④But “eating” smog and pollutants is not the only thing this skyscraper is able to do. In fact, thanks to 3D printing, the materials the building used will become even better and stronger—not only making the skyscraper look more modern, but also make it possible to stand strong winds and terrible weather.

    ⑤However, some people don't think it will work out well. Air pollution has its own character and it harms lots of cities. Does the smog-eating building have such a magical ability to stop the pollution? It seems impossible to bring the pollution under control in a short time. We should prepare ourselves for a hard fight against the pollution.

    ⑥Sounds impossible? Anyway, Arconic believes a skyscraper of this kind will be built by 2062.

    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（州）have more heart trouble after the weather changes in February or March.

    The weather can also influence intelligence. For example, in a 1983 report by scientists, 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%lower.The wind can help people have more intelligence. Very hot weather, on the other hand, 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（健忘）. People leave more bags on buses and in shops on low-pressure days. People feel best at a temperature of about 18℃.

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

    Skin-diving (自由潜水) is a new sport today. This sport takes you into a wonderful new world. It is like a visit to the moon! When you are under water, it is easy for you to climb big rocks because you are no longer heavy. Here, under water, everything is blue and green. During the day, there is enough light. When fish swim nearby (附近), you can catch them with your hands. When you have a tank (罐) of air on your back, you can stay in deep water for a long time. But you must be careful. To catch the fish is one of the most interesting parts of this sport. On the other hand, you can clean the ships without taking them out of the water. You can get many things from the deep sea. Now you can see that skin-diving is both useful and interesting.

    The world uses about a thousand million (百万) tons of water a day. Water is a human right and everyone should have their share. Yet more than 700 million people around the world have trouble getting clean, safe water.

    Treating wastewater is a good way to provide fresh water for us. And it also helps the environment by keeping waste out of rivers and oceans. 80% of wastewater around the world is not treated at all, and it is running into oceans. But now we have got the technology to treat and reuse the wastewater.

    While 75% of our planet is covered with water, only about 2% is fresh water—that comes from rivers, lakes, ice and snow. The rest, 98% of the water, is in seas and oceans. It is too salty to drink. Then desalination businesses come in. More than 19,000 factories have been built around the world, mostly in coastal countries. They process (加工) more than 92 million tons of water every day. But the technology they use requires a lot of energy.

    Scientists are working to create a less costly technology. They want to produce 20 times more clean water and make sure everyone has enough. But for now, the world still faces each day with not having enough water for everyone.