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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.

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You Can Make a Windsock(风筒)

    Have you ever seen a windsock blowing in the wind? Well, you can make one of your own! This is a fun project that you can do with things you may have. You just need to follow a few easy steps.

You will need:

●one piece of heavy colored paper   ●five ribbons

●strong tape       ●a string

●a pencil

What to do:

Step 1: Draw pictures on the paper. You can write your name on it. Do anything that will make it special to you.

    Step 2: Make the paper into the shape of a tube. Hold one of the shorter edges(边缘) over the other. Then make them together with the tape at each end and in the middle.

Step 3: Use a pencil to make a hole into both sides of the tube. The holes should be only on one end of the tube. Pull the string through both holes. Then tie the ends of the string together.

    Step 4: Now make five holes around the top of the other end of the tube.Put a ribbon through each of the holes. Tie a knot in the ends.

    Make sure the knots are bigger than the holes.

    Now your windsock is ready to use, but how does it work? The shape of the tube plays an important part. Wind blows through the tube and makes it fly and dance around. Hold the windsock up in the air by its string and run around. It will fly behind you. You can also hang it outside and watch it dance around on its own!

Pollution

    Hundreds of years ago, life was much harder than it is today. People didn't have modern machines. There was no modern medicine, either.

    Life today has brought new problems. One of the biggest is pollution （污染）. Water pollution has made our rivers and lakes dirty. It kills our fish and polluted our drinking water. Noise pollution makes us talk louder and become angry more easily. Air pollution is the most serious kind of pollution. It's bad to all living things in the world.

    Cars, planes and factories all pollute our air every day. Sometimes the polluted air is so thick that it is like a quilt over a city. This kind of quilt is called smog（烟雾）.

    Many countries are making rules to fight pollution. Factories must now clean their water before it is thrown away, they mustn't blow dirty smoke into the air.

    We need to do many other things. We can put waste things in the dustbin and not throw it on the ground. We can go to work by bus or with our friends in the same car. If there are fewer people driving, there will be less pollution.

    Rules are not enough. Every person must help to fight pollution.

    With the development of the technology, 3D printing is becoming more and more popular. We are now able to print things such as clothing, musical instruments and even cars. People and businesses are able to create the things they need very quickly and easily by using 3D printers.

    But can you imagine printing food? Some scientists are trying a new way to get the dining experience by doing this. They hope that having a 3D printer in the kitchen will become as common as the oven or blender. Scientists say that they are easy to use: you simply have to choose a recipe (食谱) and put the uncooked "food ink" into a printer. You can also change the instructions to make the food you want. This means that it would be very quick and easy to create tasty and rich meals.

    Using 3D printers to create your meals would also be saving the environment. There would be less need for traditional growing, shipping and packaging processes as food products would be a lot quicker and better. For example, tree leaves and insects could be turned into tasty products! Printing food could also help people who have a swallowing (吞咽) trouble. They could program the printer to print softer kinds of foods so that they would not have difficulty swallowing them.

            It could take away many jobs, including those for growing, shipping and packaging food. Imagine a world where there was no need for growing or producing and the same tastes could be printed from an uncooked "food ink". Besides, traditional restaurants might lose business. Also, we have to consider: is it really possible to get everything we need from them?

    As we know, cooking and eating together with family and friends has long been a traditional and enjoyable activity. It is hard to imagine a world where the pastime of cooking is dead and meals can be created at the touch of a machine.

    Albert Einstein is right once again! He thought of the idea about gravitational waves years ago with his Theory of Relativity, but scientists are finally discovering that it really exists now. But what are gravitational waves, and why are they important?

    Well, gravitational waves are made by black holes and can change time in space. Black holes aren't holes but are lots of matter put together into a very small area. They are created when a star, much like our sun, explodes and leaves behind this dense* material. It doesn't shine like a star any more, and it becomes black.

    The black holes that made these waves are special. About 1.3 billion years ago, there were two black holes that kept moving closer and closer together. Finally, they hit each other and formed one big black hole. The energy is given off and created the ripples* in space. These ripples are gravitational waves. For example, imagine you throw a stone into a pool. It creates ripples that change the shape of the water. Well, that's kind of what the influence of one black hole hitting the other has in space.

    Gravitational waves are hard to explore. But thanks to the efforts of scientists, the ripples were discovered on Feb. 11th, which is the first time in human history. Einstein was excellent to know this 100 years ago before we have the technology. It can give us a new view of the universe we live in. The discovery of gravitational waves, unlike stars, galaxies and other bright objects, black holes don't produce light, so we can't see them by tools. Gravitational waves allow scientists to look at the universe not only with light, but also with gravity. "Everything else in astronomy like the eye," A scientist told The New York Times. "Finally, astronomy grew ears. We had never ears before."

    Now, we will be able to find black holes and things that are much further away from Earth, which means much more space exploration in the future. And who knows, this discovery could even lead to time travel!

    If you go shopping in any toy store, you can see clearly the differentgames and toys for boys and girls: there are a lot of pink toys on one side ofthe store for girls; and dark colored cars, guns, and soldiers for boys. Somebig stores with toys may even have a pink floor for girls and a blue floor forboys. In fact, it is difficult to buy a toy for a girl that is not pink.

    Somepeople think that too much pink is bad for girls. Sue Palmer, writer of ToxicChildhood, is very worried that most girls over the age of three are crazyabout the color. According to some scientists, this happens for two reasons. Firstly,most companies offer too many products in pink. Also, many parents think theirlittle daughter looks cute in pink. Sue Palmer says that girls at this agecannot make proper decisions by themselves, but the pink can affect (影响) the choices and thedecisions they will make in the future.

    Someparents are worried too-for example, Vanessa Holburn, thirty-two, who has twogirls under the age of four. Their bedrooms are a sea of pink and Vanessa isnot happy. "Pink says that you are soft and gentle. Blue says that you arestrong and powerful. I want my daughters to be strong and powerful. I'm worriedthat pink will not help them with that,"she says.

    Butnot everyone thinks there's something wrong with pink. Grayson Turner is afather of three girls and he isn't worried at all. "People forget thatthings change all the time," he says. "My girls used to love pink whenthey were little, but as they get older, they change." Turner explainsthat his twelve-year-old daughter never wears pink clothes anymore. "Thislove of pink is just a fashion and all fashions change," he adds. "It'sonly since the 1940s that people have started dressing girls in pink-beforethat it was a color for boys."