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   Cats are the most popular pets among Americans. So it is not surprising there are many expressions about cats. Do you know any of them? Now let me introduce some to you.
   Some cats like to catch small birds, like canaries. If someone looks very proud or satisfied with himself, we say he looks like the cat that ate the canary.
   Sometimes, a cat likes to play with a small animal it catches. So if you play cat and mouse with someone, you change between different kinds of behavior when dealing with another person. For example, a child might offer something sweet to her little brother, and then take it away when reaches for it.
   A cat will often catch a small animal and present it to its owner. The saying “that looks like something the cat dragged in (把…拖进来)” describes something in bad condition.
   A fat cat is a person with a lot of money.
   There are many other expressions about cats in America. How interesting! Which kind of cat are you, or which kind would you like to be?

      Our factories and homes burn coal and oil. Every year we have forest fires somewhere. Many scientists believe that the weather is changing.

      The earth will perhaps be warmed by about 7℃ at the South Pole(极) and the North Pole. The ice will be melt(融化). The sea level(平面) will rise by about 7 meters. As a result, water will cover cities like London, Tokyo and New York. Some ports(港口) and towns along the coasts will disappear under water.

      Some other scientists think that the dust, smoke and pollution from coal, wood and oil fires will block out(封闭) the ultraviolet rays(紫外线). Then the earth will become colder and great sheets of ice will cover Europe and North America.

      When chemicals in the air mix with rain, we have acid(酸) rain. Acid rain can bring us great harm. It destroys(破坏) forests and kills life in lakes and rivers.

      People are beginning to see how serious the problem is. They find it important to work with nature instead of against it. They are trying to save the earth in many different ways. But one of the most important things to do is to make people understand that saving the earth is saving ourselves.

    In nature，you may see many insects and animals of different colors．Have you ever wondered why?

Locusts(蝗虫)are super delicious food for birds，but it is not always an easy job for birds to catch them．It is neither because locusts are good jumpers or runners nor because they are smarter than their enemies．The reason is that the colors of locusts change with the colors of crops(农作物)．When crops are young，locusts look green．But when autumn comes，locusts change to the yellow and brown color as crops do．

    Brown bears，tigers and other animals move quietly through forests．They can't be seen easily by their enemies．This is because they have colors similar to the trees．For the same reason．polar bears that live on a land of snow and ice are white．Butterflies and bees living among the flowers are colorful like flowers．Soil insects are mostly dark—colored and they live under the soil in a dark and wet environment．However，insects with colors different from plants can easily be found and eaten by others．So in order to survive ， they have to hide themselves in the daytime and appear only at night．

    Have you ever noticed some even stranger acts? The ink fish in the sea can send out some very black ink when it faces danger．As the ink spreads over．its enemies will not find themselves suddenly in a dark world．At the same time the ink fish immediately swims away．That is how it keeps itself save though it is not strong at all．

    As everyone knows, animals are our friends. Of all the animals, dogs are friendly to 1.

    Dogs are always staying 2 human beings. They are in different colours. There are many different 3 of dogs. Hunting dogs can 4people get more prey(猎物). The seeing-eye dogs can help 5people a lot. The police dogs can help the police.

    Today it is 6 to imagine the life without dogs. Maybe everyone is happy to see dog. Dogs are good at7 and smelling. Some dogs can find the people who are trapped(困) 8 the broken house. Some dogs can help take care of the houses. 9someone strange comes close to the house, they will bark to frighten him. Even some dogs can help look after kids when their 10 are not at home.

    In a word, dogs are our best friends among all animals.

    There are some easy things you can do to protect the environment and the earth. Choose ideas from the list or come up with a few of your own.

    •Plant flowers, grass or trees.

    •Whenever you visit a park or beach, take away what you bring there—keep rubbish in a bag until you can put it in a dustbin.

    •Turn off the lights and TV sets 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.

    •Keep the doors and windows closed in winter to keep warm air in.

    •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 to protecting the environment, the world will become much more beautiful.