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    According to the World Health Organization (WHO), environmental pollution kills 1.7 million children under the age of five every year worldwide. The WHO warns that child deaths will increase greatly if pollution continues to worsen. Of all the environmental problems, air pollution is being called the most dangerous.

    Most of these deaths take place in developing countries. However, WHO environment and health chief Maria Neira tells that air pollution is a leveler between rich and poor. Everybody, she says, needs to breathe.

    “You can be a very rich child, your parents very rich, but living in a place, in a city, which is very polluted. Then there is very little you can do because we all need to breathe. Air pollution is everywhere.”

    Maria Neira says one of the most important ways to reduce air pollution is to produce cleaner fuels for cooking and heating.

    “Almost half of the world population is using dirty fuels for cooking, heating, and lighting at home. And, this is affecting very much mothers who are staying and cooking at home, but the children who are around mothers—they are exposed as well.”

    Cleaning up how the world cooks, heats and lights homes and other buildings is a big-picture goal.

    But what can every one of us do to limit our family to air pollution?

    The U.S. Environmental Protection Agency has the following suggestions:

    ● Avoid walking where there is a high volume of vehicle traffic.

    ● Equip homes with air filters and air conditioning units.

    ● Limit your time outside if you live in an area that issues warnings about air quality.

    ● Wear high-grade, rated face masks tightly to the face when air quality is poor.

    ● If you live or commute in a very polluted area, remove your clothes and wash immediately after entering your house.

    However, the WHO stresses that governments around the world need to take the lead on ensuring that children grow up in a clean environment.

    In many high schools, there are strict rules about using mobile phones. If your phone rings in class, for example, the teacher will be very angry.

    Every mobile phone has a ringtone (铃声). It tells you that someone is calling you. Now, there is a ringtone called “mosquitotone (蚊子铃声)”.

    Mosquitotone has a special sound. Only children and teenagers can hear it. As we get older, we are unable to hear some sounds with high frequencies (频率). As a result, a child or teenager can hear the mosquitotone ringtone, but someone of 20 or older can't.

    But sometimes, people over 20 can hear the ringtone. One British student's phone uses mosquitotone. In class, the student's phone rang. The 22-year-old teacher looked at the student and became unhappy. “I heard that. You know the rule：no mobile phone in class. ”

    Not all the students are interested in mosquitotone. Jerry Jones, a high school student of 17, says, “Using mosquitotone too often is bad for our hearing. I may use it for pleasure, but not in class. It's unfair(不公平的) to the teachers！”

    What do parents think of mosquitotone？“I think it is perfect for places like movie theaters,” says Connie Neeson, 44. “Think about it. You're watching a film and someone's mobile phone rings. Mosquitotone is good because many people don't hear it. However, it also has a bad influence（影响） on their study if students use it in class. ”

    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.

    There are over 37 000 known kinds of spiders（蜘蛛）in different shapes and sizes in the world. The largest spiders live in the rain forests of South America and are known as the "bird-eating" spiders. These spiders can grow up to 28cm long and they eat small birds. The smallest spiders are from Western Samoa. These tiny spiders are less than 0.5mm long. They live in the plants that grow on mountain rocks.

    Some people like to keep spiders as pets but most people don't like touching them. A great number of people are afraid of them mainly because of their poison—something will make them hurt or even die. But in fact, only thirty kinds of spiders are very dangerous to humans. Spiders provide benefits for humans by catching and eating insects such as flies and mosquitoes (蚊子).

    Spiders are different from other animals because they make webs to catch the small insects for food. The special silk of a spider's web is light and strong—five times(倍)stronger than steel. Some people have tried to raise spiders in order to collect their silk but no one was successful in doing it. One reason is that it takes 670 000 spiders to produce half a kilo of silk and all of these spiders need living insects for their food. Besides, spiders are usually solitary (独自的) animals and they need keeping alone.

    All in all people are amazed to learn that there are so many secrets in spiders!

    For thousands of years, humans have explored(探索)the Earth. Nowadays, we are exploring space. Astronomers (天文学家) are the modern﹣day explorers, Now, many astronomers are looking for new planets and new places for humans to live in the future. But where do astronomers start looking？

    First of all, astronomers look for a star. That's because our own Earth moves around a star (the Sun). More importantly, it is the correct distance( 距离) from the Sun for heat and light. So when astronomers have found the star, they look at the planets around it. In recent years, astronomers have found nearly 400 new planets with stars. However, many of these planets are either too near to the star or too far away.

    However, if the planet is in a good position, astronomers look for three key things: water, air and rock. Water is important because all life needs water. Humans can drink it and they can also grow plants with water. And plants produce air for humans to breathe and food to eat. Rock on a planet is also important. That's because there is often water under the rock.

    After many years of scrutinizing, astronomers have found a planet that is similar to the Earth. It's Gliese 581g and it's near a star. The astronomers think it has water and rock and the average(平均的) temperature is between -31℃ and -12℃.That's cold, but not colder than Antarctica or the Arctic Circle, for example. Gliese 581g is bigger than the Earth. A year on Gliese 581g is only 37 Earth days instead of 365. But astronomers do not think these are big differences and some of them think Gliese 581g will be a new Earth. However, Gliese 58Ig is twenty light years from the Earth.