It's very important that we all recycle.In nature,everything1 again.For example,when an animal dies,it becomes2 animal's food.Nothing is wasted.But humans have created things like plastic bags which can't be3 down by nature.Our4 kills animals and pollutes water and soil.5 we continue making too much rubbish,the problem will only get worse.If nature can't reuse the rubbish,we must recycle6 .We should clean up the rubbish we've made because nature can't.

    Recycling is also the right thing to do for another reason.The earth is rich in natural materials like water and trees,7 these materials are not endless (无尽的).We use up our natural materials8 faster than the earth is able to reproduce (再生) them.For example,each year we cut9 more than 6,000 square miles of forest.But it takes an average of 25 years for a new tree10 .

    Recycling can help us save the earth,so let's take action right now.

    The undersea world is very beautiful. Now more and more people want to 1 in the water to find the secret there. Scuba diving (水肺潜水) is a new sport today. It can take you into a wonderful undersea world.

    If you are lucky, you will 2 find many strange animals in the sea. Some are as 3 as a school bus. Some are so tiny that you may not  4 them at all.

    During the day, there is enough 5. Everything is blue and green. When fish swim nearby, you can catch them with your hands. When you have bottles of air on your back, you can stay in 6 water for a long time. However, you can't dive too deep. And you must be very 7 when you are in deep water, because something dangerous may happen unexpectedly.

    The deep sea is not an easy place to live in. It's cold, and it's 8 too. The deeper it is, the less sunlight there is. At about 3,000 feet, there is no light at all.

    Besides the cold and darkness, deep-sea animals face a third 9 —other animals. Animals eat! Many animals eat plants. However, some animals eat 10. This means these sea animals have two big jobs. They need to find animals as food, and they have to try not to become other animals' meal.

    When you hear the word "scientist", what do you think of it? Many people think scientists are people in clean white coats, working in labs( 实验室). Some scientists do work in labs. But there are 1 scientists working in woods and jungles(丛林).  These scientists are called " animal behaviour (行为) scientists", and they study animals as they live in nature. Why don't these scientists catch animals and study them in zoos? The 2 is in the word "behaviour". Animal behaviour scientists want to learn 3 animals behave in their wild homes. When animals live in cages or in zoos, they do not act 4 as they do in the wild. They may fight (打架) 5each other, or they may not eat, or they may not raise (抚养) their babies as they usually do. To see real animal behaviour, scientists must go to the places 6the animals live. So animal behavior scientists go into the jungles, the woods or the deserts. There, 7most important tools are their eyes and ears. They watch and listen to the animals very 8. They write down everything that happened in notebooks. Though they live near the animals, the scientists are careful not to frighten them. If the scientists are 9, the animals will pay no attention to them. Then the scientists can see how the animals really live.

    The animal behaviour scientists hope what they've learned about animal behaviour can provide clues(提供线索) 10people learn to live with animals together more happily.

    There have been many great inventions that change the way we live. The first great 1was one that is still very important today-the wheel. This made it easy for man 2heavy things and to travel long distances. For hundreds of years after that, there were 3inventions that had as much effect as the wheel. Then in the early 1800's the world started to change 4. There was little unknown land left in the world. People did not have to explore much anymore. In the second half of the 19th century many great inventions were made.      5them were the camera, the electric light and the radio. These have all become a big part of our life today.

    The first part of the 20th century saw more great inventions. The helicopter in 1909. Movies 6sound in 1926. The computer in 1928. And jet planes in 1930. This was also a time when a new 7was first made. Nylon came out in 1935. It changed the kind of clothes people wear. Of course new inventions continued to be made. Man began looking 8 ways to go into space. Russia made the first step. Then the United States took another. Since then other countries，including China and Japan,9their steps into space. In 1969 man took his biggest step away from earth. 10first walked on the moon. This was certainly just a beginning. New inventions will someday allow us to do things we have never yet dreamed of.

    Researcher Robert Engelman from Population Action International says by the year 2025 about 3000 million people may lack water. At least 18 more countries are expected to have serious water problems. The need for water keeps increasing.

    Mr Engelman says the population in these countries that lack water is growing faster than in other parts of the world. The report says lack of water in the future may result in(导致)several problems. It may even increase1problems. Lack of water often means drinking water isn't safe. Mr Engelman says there are problems all over the world because of diseases, Lack of water may also2more international con flint(冲突), Countries may have to compete for water in the future. Some countries, such as Egypt, the Netherlands, Cambodia, now get sixty percent of their fresh water from other countries. And the report says lack of water would affect(影响)the ability of developing to improve their economies. This is3new industries(工业)offer need a large amount of water when they are beginning.

    The Population Action International study gives several solutions4the water problem. One way, it says, is to find ways to use water for more than one purpose.5way is to teach people to be careful and not to waste water. A third way is to use less water of agriculture, The6also says long-term(长期的)ways of dealing with the water problem must include controls on population growth.