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    Have you ever had dreams about building a robot? Or putting together a spaceship? Or even seeing your face made out of chocolate? Done. All you need is a 3-D printer.

    The possibilities of 3-D printing seem endless(无穷尽的）.All the user has to do is to design an object on the computer and choose a material to print in. The printers print in hundreds of different materials including glass, sugar and even skin! When the user presses(按）“print", the 3-D printer spreads the materials layer(层）by layer and like magic the object is produced.

    The first 3-D printer was invented in 1986 by an American, Charles Hull. But 3-D printing has only become cheap enough recently for most people to use. Designers now use 3-D printing to create unusual things. The Dutch artist Dirk Vander Kooj prints furniture made from old fridges. And doctors have used 3-D printing to print human body parts! The Telegraph reported in February that scientists from Cornell Medical College even printed a man-made ear.

    But like a lot of new technologies, if 3-D printing gets into the wrong hands, it can be dangerous.

    In 2011 a group of four men in the US used 3-D printing to produce ATM skimmers(提款机盗刷器).These were placed on an ATM and stole over $400,000 from users of the ATM. It is terrible to think that criminals like them might one day use a 3-D printer to print a gun.

    But for better or for worse, 3-D printing has been put into use. In a few years, you'll probably be wondering how you could ever live without your 3-D printer!

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    When you look at the sky at night, the Moon looks bigger than the stars. Actually (实际上), the Moon is much smaller than the stars and the Sun. It's much smaller than the Earth. But the Moon is much closer to us than any star. That is why it looks so big. If you hold a coin close to your eyes, it looks big. If you look at it across the Moon, it looks small.

    The Moon moves around the Earth. It makes one trip in about four weeks. The Moon looks flat to us. But it is a round ball, like the Earth.

    People once thought the Moon had fire (火) on it. They thought the fire made it bright. Now we know the Moon is like a mirror. It gets its light from the Sun.

    Our sunlight comes from the Sun, too. What is the Sun? The Sun is a star. The stars we can see have their own light. There are many big stars we cannot see. Their light has burned out. Others are still bright, but they are so far away that we cannot see them. The Sun looks bigger and much brighter than other stars in Galaxy because it is the nearest of all stars. The Sun and the other stars we see are very hot, but the air around us saves us from the heat of the Sun.

    The Sun gives us light and warmth (温暖). It makes plants grow and turns leaves green. It makes life possible on the Earth. It is a life giving star.

    When we think of paper, we think of newspapers and books. But there are many other uses. Only half of the world's paper is used for books and newspapers.

    Paper is very good for keeping you warm. You have perhaps seen homeless men sleep on a large number of newspapers. In Finland, it is sometimes-40℃ in winter. The farmers wear paper boots(靴子)in the snow. Nothing could be warmer.

    Each year, more and more things are made of paper. We have had paper cups and plates for a long time. But now we hear that chairs, tables, and even beds can be made of paper. Besides paper boots and shoes, you can wear paper hats, paper dresses, and paper raincoats. When you have used them once, you may throw them away and buy new ones.

    The latest use of paper seems to be paper houses. These are not small houses for children to play in, but real, big houses for people to live in. You can buy a house with three rooms for about 500 dollars. You can put it up by yourself in a few hours, and you can use it for about five years.

    How do you deal with plastic bags from the supermarket? Throw them away or recycle them? How about eating them?

    The bags are not harmful to the environment, Humans and animals can safely eat them. Indian company EnviGreen has made a bag with natural materials. It looks and feels just like plastic, but can break down(分解) easily.

    Ashwath Hedge who set up the EnviGreen Company spent four years doing experiments(实验) with 12 natural materials. They include potato, corn, vegetable oil and banana. He made the materials into liquid(液体) and used the liquid to make the bag.

    Although the EnviGreen bag is more expensive than a common plastic bag, it has many advantages. According to the Wall Street Journal, it takes 1,000 years for common plastic bags to break down. But an EnviGreen bag can naturally break down in less than 180 days. It also breaks down in less than a day in water, and in less than a minute in boiling water. Hedge was happy to show it in his interview, he put an EnviGreen bag in water and ate it with a smile.

    There are more than 15,000 tons of plastic waste in India every day. But only 9, 000 tons are processed. In China, 3 billion plastic bags are used every day. Maybe the EnviGreen bag could be a solution(解决方法) to the world problem of plastic pollution.

    When I was a little girl, my family lived in the countryside. There was a beautiful river near my home. The water was clean and cool. I liked to go fishing there with my mother. We would catch fish, look for clams(蛤)and play in the water. There were also a lot of birds near the river. We would spend all day watching the birds.

    Now my family live in the city. Last Sunday, my daughter asked me to take her to see the river I was always talking about. "I want to go fishing there so much with you and Grandma," she said.

    When we went to the river, we only saw a factory and a mountain of waste. My mother was surprised, my daughter was disappointed, and I was sad. The river was my best friend. I grew up with it. Now there are no fish in it, and the birds have gone too. I hear them crying for help. But what can I do?