The world is not hungry，but it is thirsty. It seems strange that nearly 3/4 of the earth is covered with water while we say we are short of (短缺) water. Why? Because about 97% of water on the earth is sea water which we can't drink or use for watering plants directly. Man can only drink and use the 3%—— the water that comes from rivers and lakes. And we can't even use all of that， because some of it has been polluted.

     Now more water is needed. The problem is: Can we avoid a serious water shortage (短缺) later on?

     First we should all learn how to save water. Secondly，we should find out the ways to reuse it. Scientists have always been making studies in the field. Today，in most large cities water is used only once and then runs to the sea or rivers. But it can be used again. Even if every large city reused its water，still there would not be enough. What could people turn to next?

     The sea seems to have the best answer. There is a lot of water in the sea. All that needs to be done is to get the salt out of the sea water. This is expensive， but it's already used in many parts of the world. Scientists are trying to find a cheaper way of doing it. So you see，if we can find a way out，we'll be in no danger of drying up.

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    Do you know why different animals or pests(害虫) have their special colors? Colors in them seem to be mainly used to 1 themselves.

    Some birds like eating locusts(蝗虫), but birds cannot 2 catch them. Why? It is because locusts change their 3 with the change of the colors of crops. When crops are green, locusts look 4 But as the harvest time comes, locusts change into the same brown colo 5 crops have. Some other pests whose colors are 6 plants are easily found and eaten by 7 So they have to hide themselves for lives and appear only 8 

    If you 9 animals' life, you'll find the main use of colors is to protect 10 Bears, lions and other animals 11 quietly through forests. They cannot be easily seen by hunters 12 their colors are much like the trees.

    Colors are useful not only on the land, but also in the 13 A kind of fish can 14 （液体) when they face danger. The liquid spreads over quickly, so they cannot be found by their enemies and can quickly swim away. That is 15 they can live safely though they are not strong at all. So colors are really useful to animals.

    Audio digital books(有声图书) are becoming more and more popular these days. One of the reasons for this is that audio digital books can be "read" in many places comfortably.

    The first favorite place of many people is in bed, before going to sleep. Many people like to just lie in bed in the dark before they fall asleep at night. This would be the perfect time to listen to an audio digital book. If you read a usual book, the lights have to be turned on and you have to turn the pages with your hand. An audio book can just be listened to while a person stays comfortably in bed.

    The next favorite place to listen to audio digital books would be in the kitchen. For some people, kitchen chores are boring. Audio digital books provide good entertainment, and people don't need to turn pages.

    An audio digital book is a favorite while a person is gardening. It can help take a person's mind off the job at hand. It can be fun and exciting to do gardening with the help of the book.

    An audio digital book is a favorite while a person is exercising. It allows the mind to be free while the legs, body and arms are kept busy. This would be a great place to listen to these books.

    There are lots of objects that we see in the sky. During the day we see the sun. After the sunset in the evening, we see mostly the stars. Not all the lights in the sky that we see are really stars.

    Of course, we see the moon. Some of the other lights in the sky are planets. Planets revolve (转动) around the sun like earth does.

    Once in a while someone will see what they call a shooting star.

    Shooting star looks like a star that is moving quickly across the sky. Some people believe that seeing a shooting star will bring them good luck. It's hard to find shooting star because they disappear fast.

    The correct name for a shooting star is meteor. Besides very large objects like stars, planets and moons, space has lots of little objects. These can be rocks in space left over from old planets.

    These objects can even be as small as dust. These objects are called meteorites(陨石).

    When a meteorite gets close to the earth, it gets pulled towards the earth by gravity. Earth is surrounded by atmosphere. Atmosphere is made up of air and clouds. A meteorite blows up in the earth's atmosphere. This makes the short bright moving light in the night sky. A meteorite thus turns into a meteor.