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.

    On May 17, 2009, according to the plan, Mike Good and I would take a space walk to the Hubble Space Telescope to repair an instrument. The power supply on this instrument had failed, so it could no longer be used. I would be the person doing the repair and Mike my assistant.

    Working in space is more difficult than you can imagine. As there is no gravity, you can't stand and any slight push can result in tragedy -you can be pushed into space, never be back.

    We got to the telescope. Before we could replace the power supply, we would have to remove from the telescope a handrail fixed with four screws. Having taken out the first three, I found the fourth stripped. I realized that the handrail would not come off, which meant we could no longer be able to replace the power supply and repair that instrument, which meant scientists could no longer look at the universe and find life on other planets.

    I tried all kinds of things, and nothing worked. Then Houston, the control centre on the earth, called up and told me to use the tape to tape the bottom of the handrail and pull it off the telescope. They said it was going to take about 27 kilograms of force for me to do that.

    I knew what it meant: The handrail could be completely pulled off and the safety tether might break, and I might therefore be pushed into space.

    Mike was next to me in his space suit but he could not take over my role. I turned and looked into the cabin where my five crewmates were, and nobody in there had a space suit on. However, I knew they were all looking at me. "Come on Mass, we are all behind you." The telescope must be repaired.

    "Bam!" The handrail came right off. The rest of the walk went well. We finally got the new power supply in. They tried it; turned it on from the ground. The instrument came back to life.

    At the edge of darkness, after about eight hours, I turned around and saw the Earth from our altitude at Hubble, 568 kilometers up. I saw the huge round pure blue globe home planet. It's the most beautiful, magnificent thing I've ever seen. It's like looking into heaven. It's paradise.

    Have you ever heard robot fish? Scientists will put some robot fish into the sea near Spain. These robot fish will help people to detect (探测) the pollution in the water. If the robot fish are able to finish their work successfully, the scientists hope to put them into rivers, lakes and seas around the world.

    The fish are about 1.5 meters long. There will be a detector in their bodies. They can find the sources (来源) of pollution in the water, and then the robot fish will eat part of it. Unlike other robots, they don't need to be controlled by people far away. The robot fish all have an eight-hour battery (电池). They can "swim" in the sea freely and send back information to people on the beach. After their batteries die, they will return by themselves.

    There are five robot fish altogether now. Each costs about 29,000 dollars. They are part of a three-year project between engineering company BMT Group and Essex University in southeastern England.

    "We invented the robot fish creatively. We hope them can find the changes in the sea water and report back the information," said Professor Hu of Essex University. His team is developing the fish.

    Many people know Shanghai's beautiful night view(景色), especially the colorful lights from the buildings. Light helps us see and makes the environment more beautiful. However, too much light becomes a kind of pollution but many of us pay little attention to this pollution or even ignore it. In fact, it causes a lot of problems. Light pollution can be almost as bad as carbon dioxide pollution.

    Too much light can do harm to our health. First, it can make us feel bad and we can't sleep well. Second, lights need electricity, and creating electricity will give off greenhouse gases. This affects the air and causes breathing problems. Third, study shows people living under bright light for long can have cancer more easily.

    Too much light may be even harmful to wild animals. Thousands of birds die from it each year. Some hit into the light buildings, because they can't see clearly in the strong light. Some birds sometimes lose their ways in the bright light Sea turtles(海龟) can't find the dark beaches to lay their eggs.

    To protect humans and wildlife, we should take measures to reduce the use of lights at night.

    Most American children eat potatoes. But many children don't know what of the potato is the best food. Take a knife and cut from the middle of the potato a piece as thin as paper. I hold the piece between your eyes and light. You will see that the potato has skin(皮), an outside rim(边缘)and an inside part. The outside rim which is right under the skin of the potato, is the most valuable part of all. But this is often thrown away with the skin. Even the skin itself is better for food than the inside. When eating a cooked potato, if you choose the inside and leave the outside, you are throwing the best part of it. If you can't cat the whole potato, eat the outside rim first and leave the inside part.

    Do you know when Earth Day is? It is on April 22nd, and it began in the US in 1970. Earth Day in our country began in the 1990s. Earth Day is a good time for people to think about what they can do to make the Earth clean and beautiful, because now the environment on Earth is getting worse and worse. In fact, there are many things we can do to protect our Earth.

    Plant trees.

    Planting more trees helps to reduce greenhouse gases (温室气体), stop the earth from running away and provide homes for animals.

    Don't waste.

    Do not waste water. Use both sides of paper when you write. Turn off the light when you leave. Take your cup with you. Take your own shopping bags to the supermarket. Stop using the plastic bags. Don't use any disposable things. We should save energy.

    Don't throw rubbish in the streets.

    When rainwater washes over the rubbish, it becomes polluted. The polluted water flows into the rivers and seas.

    Ride your bike or take a bus.

    Too many cars pollute the air and waste energy.

    Remember: Every day is Earth Day.

    We should protect the Earth every day, not just on Earth Day. The Earth is our home. Let's do our best to make the Earth cleaner and more beautiful.