Many people know that rubbish is a big problem on planet Earth. What many people don't know is that junk (垃圾) has become a problem in outer space too.

    According to BBC News, there are more than 22, 000 pieces of space junk floating around the earth. Andtheseare just the things that we can see from the surface of the earth by telescopes (望远镜). There are also millions of smaller pieces of junk that we can't see.

    Objects, like bits of old space rockets or satellites, move around the planet at very high speeds, so fast that even a very small piece can break important satellites or become dangerous to astronauts. If the tiniest piece of junk crashed into a spaceship, it could damage the vehicle.

    To make things worse, when two objects in space crash, they break into many smaller pieces. For example, when a U. S. satellite hit an old Russian rocket in 2009, it broke into more than 2,000 pieces, increasing the amount of space junk.

    To reduce additional space junk, countries have agreed that all new space tools can only stay in space for 25 years at most. Each tool must be built to fall safely into the earth's atmosphere after that time. In the upper parts of the atmosphere, it will burn up.

    Many scientists are also suggesting different ways to clean up space junk. In England scientists are testing a metal net that can be fired into space junk. The net catches the junk and then pulls it into the earth's atmosphere to burn up. The Germans are building robots that can collect pieces of space junk and bring them back to Earth to be safely destroyed.

    "The problem is becoming more challenging because we're sending more objects into space to help people use their mobile phones and computers," says Marco Castronuovo, an Italian space researcher.

    "The time to act is now. The longer we leave the problem, the bigger it will become," he says.

Music is good for us. According to the new study from the World Health Organization (WHO), music can 1 us happy and healthy. For example, when I feel 2 listening to some classical music helps me relax. When I'm down, I like pop music full of hope and love. It is easy for 3to fall asleep with light music. Some doctors 4 that people who love music may have a long life.

Near my house, a man and his wife have a small music house with mood music(情调音乐). People like to spend time here when 5are plying different kinds of music. Sometimes, we are lucky to hear some famous singers sing songs written by themselves. The songs are 6beautiful that we sing along with them. We communicate(交流)with one another 7 his special language. The most moving music is Chinese folk music(乡村音乐). It 8_us the sweet days in the past.

Everyone of us, rich or 9, young or old, may have his favorite song. 10 will be together with us as long as we live.

Every living thing needs to reproduce（繁殖）. Reproducing means creating more members of your group. In order for plants to reproduce, they have to spread their seeds（种子）to other areas. Plants have developed all kinds of ways to do this.

The simplest way is gravity（重力）. Many seeds are inside of fruit. When fruit gets too heavy, it falls from a tree to the ground. Sometimes animals will pick up the fruit and drop it in another area. That helps move the seed even farther away. Apples spread this way.

Other plants use wind to spread their seeds. Dandelions（蒲公英）are a good example of this. Dandelion seeds are so light that when wind blows, it carries dandelion seeds to new places. Maple（枫树）seeds also use wind. Their seeds are connected with long, thin leaves that look like wings. When the seed falls from the tree, its "wings" help it fly farther from the tree.

Some animals help plants spread their seeds. The animals eat the seeds. While the seed is in the animal's body, it stays whole. When the seed leaves the animal, it's in a new place.

Ants also help spread seeds. Some seeds have a special smell that appeals to ants. The ants bring the seeds back to their home, which of course is underground. They only eat part of the seed. They leave the rest of the seed underground. After that, the seed can start growing.

We have learned English for several years, so we can read English books and magazines without the teachers' help. We feel good when we finish 1 an English story or a whole book 2 ourselves. But3 can we be a better reader?

It is important 4 some suitable books. Then what books are suitable? Well, I think we should first choose books that are not too difficult or too 5 . Then when we are reading, we should 6 let new words take too much of our attention. Just do as we often do in our own language. While we are reading, try to 7 the meanings of the new words, and try to decide which of the key words we could guess and which we have to 8 in the dictionary.

If we follow these 9 , we will be10 in reading English books and magazines.

The Spring Festival(春节)is coming.You will buy new clothes and much food.There are always some old clothes you don't want.And there is always some food you can't eat.What can you do?Take them to two places(地方)，

In a high mountain area in central Utah stands the world's oldest, heaviest and largest tree, Pando. And it's dying!

Pando means "I spread" in Latin and it's a name that makes sense. Pando is a big group of trees that all grow from the same roots(根). They look separate but are all joined underground by their roots. With all these roots joined, the whole group of trees can share water and food. 

    ▲    . In summer, animals(mule deer and cattle) feed on the new leaves, making it difficult for the trees to grow. The number of mule deer has even increased because their natural enemies(mountain lions, bears) have disappeared. The second problem is from people. Hikers and campers like this area because of the colourful leaves in autumn. But getting too close and stepping on the new growth has made Pando smaller and thinner over the last 50 years. 

Protecting Pando is challenging. Putting fences(栅栏) around it to keep animals away has helped new growth. But deer are smart, and they've found ways to get through the fences. Other efforts have included cutting or burning part of Pando to encourage new growth. Pando grows back very quickly after a forest fire, and these fires do not reach temperatures that would kill its root system. 

Michael Grant, one of the scientists who helped name Pando, warns if the trees are in trouble, the whole ecosystem will be in danger too. We need to make people understand the long-term effects of our actions.