Tigers are very strong and scary. We may see tigers in Europe, Asia and America in the mountains. The tigers live far away from {#blank#}1{#/blank#} houses. They eat birds, hares (野兔) and other small {#blank#}2{#/blank#}. In the day they hide in the dens (巢穴), and at night they go out {#blank#}3{#/blank#} food.

    In {#blank#}4{#/blank#} when tigers are hungry, they will become very {#blank#}5{#/blank#} But now, people cut down many {#blank#}6{#/blank#}, so tigers are losing their homes. Also, some people kill tigers to get {#blank#}7{#/blank#} fur. Some people even buy things made {#blank#}8{#/blank#} tiger bones (虎骨). So the number of tigers {#blank#}9{#/blank#} getting smaller and smaller.

    Animals are our {#blank#}10{#/blank#} friends. In order to protect them, we must build many natural reserves. And we must stop people from hunting.

    When the weather is hot, you go to a lake or an ocean. When you are near a lake or an Ocean, you feel cool. Why? The sun makes the earth hot, but it cannot make the water very hot. Although the air over the earth becomes hot, the air over the water is still cool. The hot air over the earth goes up. Then the cool air over the water moves in and takes the place of the hot air.

    Then you may ask, "Why is the ocean full of salt?" Scientists will say that the salt comes from the rocks. When the rocks get very hot or very cold, they crack (爆裂). Rain falls into the cracks. The rain then carries the salt into the earth and into the rivers. The rivers carry the salt into the ocean. And then you may doubt, "But the ocean does not get more salty every year. Scientists are not sure about the answer to this question.

    We know a lot about our world. But there are still many answers that we do not have, and we are curious about them.

    Electricity is an important part in our life. We can't see or touch it, but it is all around us. Our life will be terrible without electricity. But some people don't know that everyone should save electricity. When it is not completely dark, many street lamps (路灯) light up early in some streets. Some people don't turn off the lights when they leave the room. Some people are sleeping with the lights on. They are all wrong. Here I make some suggestions about stopping these things:

    *Turn on the street lamps on time. We light them from 7：00 p. m.～5：30 a. m. in summer, and from 5：30 p. m.~6：00 a. m. in winter.

    *If some small areas are very dark, just turn on a few lights.

    *The distance (距离) between street lights can be 50～60 meters. It can save electricity and money.

    *If there are some activities, such as fairs, we can make the lights bright；if there is no activity, lights needn't be too bright.

    Ask people to save electricity through TV shows, newspapers, and so on.

    Electricity is a valuable resource (资源). It helps us live well and conveniently. We should take action to save it at once!

    How green are you? Do you know how to be green?

    We all need a healthy environment, but we produce waste every day and it does harm to our environment. Though we are young, we can still do something to help. In fact, even the simplest everyday activities can make a real difference to the environment. Here are some ideas for you.

    Reduce

    Reduce means "use less". Don't waste things. This saves money and reduces pollution and waste going into the environment. Before we buy something new, think whether it is really necessary—or maybe the old one will be just as good! When we buy things, choose local products if possible, and try not to buy too many things from abroad.

    Reuse

    Reuse means "use again". Use things for as long as possible. When we buy things, make sure that they last a long time. We should look after them so that they will last, and we should repair them if we can instead of throwing them away and buying new ones. Don't use a paper cup or a paper bag. It's better to use a china (瓷器) cup and a lunch box because you can use them again.

    Recycle

    Recycle means "change things into something else". Though it takes energy to change something into something else, it's better than throwing things away or burning them. Find out what can be recycled in your neighbourhood and take part in recycling programmes. We should also buy products made from recycled materials, such as recycled paper, to help save trees.

    So please remember these three words: reduce, reuse and recycle.

①Eating good food and getting proper exercise are important to stay healthy. Getting enough sleep is important, too. Experts say that teenagers between the ages of 15 and 20 need 8 to 10 hours of sleep each night. 

②Your body needs to take a rest from all the activities it has done during the day. Your brain needs a rest, too. You are likely to get sick easier without enough sleep. 

③You have a "24-hour clock" inside your body that tells you when to be awake and when to go to sleep.  ▲  Blue light that comes from the Sun tells your brain to keep you awake during the day. When there is no blue light at night, the brain tells the body that it's time for sleep. 

④There are many things that stop the brain from telling your body when it's time to sleep. One of these is blue light at night. Today, people spend a lot of time watching television or looking at screens on computers or smart phones. These devices (装置) give off blue light. If you look at them at night, the blue light can trick your body into thinking it's daytime. Then it is more difficult to go to sleep.

⑤What should you do to get good sleep? Experts say that you shouldn't look at screens that give off blue light for at least one hour before going to sleep. 

⑥ Do not watch TV or use anything with a computer screen in bed. If you need to do something to fall asleep, it is better to read a book. Also, keep your bedroom as dark as you can. This will help you sleep well.