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    Gardening is popular in many parts of the world. It brings us sweet smelling flowers, fresh fruit and vegetables. But you can get more from your garden.

    Gardening helps to keep healthy. Today's people sit indoors for too long and don't get much exercise. When you garden, you have to move around. It's a good chance for you to exercise your body by watering flowers or doing some digging. Besides, when you are in your garden, you can feel the warm sunshine. This means you are getting Vitamin D. It helps your bodies use calcium (钙), which is necessary to keep your bones (骨骼) strong.

    It gets them off computers, televisions and phones. Gardening can be a great teacher to teach children about nature and healthy eating. It can also help them to understand the meaning of “No pains, no gains.”

    Gardening is a great way to meet people and build relationships. When you are gardening, you are outdoors. So it is a perfect time to communicate with your neighbors. Most people love to talk about their hobbies, and so do gardeners. They usually enjoy showing people what they are growing. And most enjoy sharing advice and stories about their gardens.

    Building an app is a big project. If you want to build the next great smartphone app, you need a plan. First, think about the kind of app that you want to build. Will your app be a game? Will it be for business? Then make a schedule(日程安排)for building the app. You need plenty of time for research before you are ready to build.

    Now you're ready to make the app. Building an app is like a puzzle(拼图)with many different parts. You can build it yourself or find a company to help you. There are many videos and websites that can teach you to build one. Some websites provide "building blocks" for app developers. As you build, you pick blocks from the website and put them in your app.

    After you build your app, you need to check it carefully. Look for bugs. Most apps have several problems to fix. Show your app to people. Ask their opinions. Mike sure everything works before letting people download it. There are so many tools that can help you build apps. Having the right tools will make the work easier. Now almost anyone can make a new app.

    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.

Everybody dreams. But only some people remember their dreams. Our dreams often include all the senses —- smells, sounds, sights, tastes and things we touch .Sometimes we dream the same dream over and over again.

    Early in the twentieth century, two famous scientists developed their personal ideas about dreams. Austrian psychiatrist (奥地利心理学家) Sigmund Freud wrote a book called "The Interpretation (诠释) of Dreams" in 1900. Freud believed people often dream about things they want but can't have. Swiss (瑞士) psychiatrist Carl Jung worked closely with Freud for several years, but he believed dreams provide solutions to problems we face when we are awake.

    Other researchers are studying how dreaming helps our bodies work with problems and very sad emotions (感情). Robert Stickgold is a professor of psychiatry (心理学教授) at Harvard University in Massachusetts. He says that when we dream, the brain is trying to make sense of the world. He does not agree with Sigmund Freud that dreaming is the way we express our hidden feelings and wishes.

    Scientists believe it is important to keep researching dreams. Doctor Stickgold says it's more than one hundred years since Sigmund Freud wrote his important book about dreaming. Yet there is still no agreement on exactly how the brain works when we are dreaming or why we dream.