There are many kinds of animals that live in the forest, such as mice, rabbits, squirrels, bears.

    Animals in the forest depend on（依靠）one another for food. Many small forest animals, such as mice, eat green plants for food, and then larger animals eat them. This is called food chain. A food chain begins with the sun. The green plants in the forest use the sun's energy to make food for themselves. It's called photosynthesis(光合作用). Mice eat flowers and seeds that forest plants produce(生产).The mice get their energy from the plants, and the mice become food for a larger animal, such as the hunting hawk. So the energy from the sun passes from the plants to the mice to the hawk. A break（中断）in any part of this food chain means some animals may not have enough food to eat.

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    Body language is one of the most powerful means of communication, often even more powerful than spoken language. People around the world show all kinds of feelings, wishes and attitudes that they might never speak aloud. It is possible to ―read‖ others around us, even if they do not want us to catch their unspoken communication. Of course, body language can be misread, but many gestures and actions are common.

    The most common facial expression is, of course, the smile – its function is to show happiness and put people at ease. It does not always mean that we are truly happy, however. Smiles around the world can be false, hiding other feelings like anger, fear or worry. There are unhappy smiles, such as when someone ―loses face‖ and smiles to hide it. However, the general purpose of smiling is to show good feelings.

From the time we are babies, we show unhappiness or anger by frowning (皱眉头). In most places around the world, frowning and turning one's back to someone shows anger. Making a fist (拳头) and shaking it almost always means that someone is angry.

How about showing that I am bored? Looking away from people or yawning will, in most cases, make me appear to be uninterested. However, if I turn toward and look at someone or something, people from almost every culture will think that I am interested.

    Being respectful to people is subjective, based on each culture, but in general it is probably not a good idea to give a hug to boss or teacher. In almost every culture, it is not usually good to stand too close to someone of a higher rank (等级). Standing at a little distance with open hands will show that I am willing to listen.

    With so many cultural differences between people, it is great to have some similarities in body language. We can often be wrong about each other, so it is an amazing thing that we understand each other as well as we do!

    The earth is about 4,600 million years old. Modern man has lived on the earth for only 35,000 years, but during that time, we have changed our planet in many ways. Many of the things that we have done are good, but more are not good for the earth.

    Water pollution

    A lot of people, birds and fish die each day because of water pollution. Factories have polluted the land and the water. As a result, many river and lakes are now dead.

    Air pollution

    In big cities, factories, as well as cars, trucks and buses are the biggest cause of air pollution. Many people in cities now have bad health problems. For example, Mexico city used to be a beautiful sunny capital, but today it is almost covered by thick brown clouds.

    Soil pollution

    In order to have a good harvest, most of the farmers use chemicals too much on their fields. That's bad for the soil. But this kind of pollution is difficult to stop.

    Hope for the future

    These problems are very serious for our future, so all of us should do something to improve our environment. If we can stop pollution, our planet will become more and more beautiful and our health will be better. Let's be greener people.

    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.

    Imagine a perfect day: the weather is good and everything seems fine. When, suddenly, your mobile phone loses its signal, the television has no programs, and you can't get online with your computer.

    What has happened? These are just the types of problems a solar storm（太阳风暴）might cause. You may not think of storms as putting our society in danger. But today, a solar storm is as serious as other bad events, such as earthquakes.

    A solar storm is caused by solar flares（太阳耀斑）: large explosions（爆炸）near the sun that can give off lots of energy. The strong energy can stop the satellite systems（卫星系统）that control our computers, telecom networks and so on. These storms can even cause the power to go out for weeks or months.

    In the past few months, scientists have recorded some of the strongest sun flares in years. The most recent one happened around Valentine's Day, 2011. It caused radio and satellite signals to go down in some northern cities in China.

    “Solar flare activity is going to be much worse than what we've seen in the past. We're not talking about a few cities losing power, it could be half of the country, maybe more.” SolarStormWarning.com, a US website about space weather, warned.

    Scientists say that little can be done to predict such a storm. Governments around the world are trying to work together before the next storm, although they are not sure when that may happen.

    There are some easy things you can do to protect the earth:

    •Plant flowers, grass or trees.

    •Whenever you visit a park or beach, take away what you take there. Keep rubbish in a bag until you can put it in a dustbin (垃圾桶).

    •Turn off the lights and TV set when you leave the room. This can save a lot of electricity.

    •Turn off the tap when you brush your teeth. You can save some water by not letting it run. Also, use a glass cup instead of a paper cup because this saves paper.

    •Give your old books and magazines to a library instead of throwing them away.

    •Give your old clothes to poor children you know instead of throwing them away.

    •Use both sides of paper.

    •Stop pouring dirty water into the rivers or lakes nearby.

    •Encourage all your friends to do the same things you do to help protect the earth.

    You don't have to wait until Earth Day to do these things. Make every day Earth Day. If everyone makes a contribution (贡献) to protecting the environment, the earth will become much more beautiful.