Are you able to send a letter with pictures and sounds to someone somewhere in the world without a stamp(邮票) on it? Using a computer you can send e-mails quickly and easily. The post is much slower than e-mail. E-mail can send its message to the other side of the world in seconds.

    E-mail is easy to use and it saves time and money. The differences in time in different parts of the world do not matter when sending e-mail. It's twenty-four-hour service(服务) that you can send e-mail at any time of the day or night. No one has to be there to get e-mail. It does not matter if your friends are in beds when you send e-mail to them, or you are seeing a movie at the movie theater when they send e-mail back.

    Twenty years ago in Costa Rica, three girls found a baby sloth（树懒）on a road. The little animal's mother was killed by a car. These girls took the baby sloth to Judy, the owner of a hotel. Judy wanted to help, but she didn't know how to look after the sloth, so she called the zoo. With the help of the zoo, Judy took good care of the baby sloth. She named the baby sloth Buttercup.

    After her success, more people brought Judy wounded sloths or baby sloths they found. Judy then opened a rescue centre（救助中心）. Today, the rescue centre has saved more than 500 sloths. Sloths live in the forests of Central America and South America. They hang on to the trees with  their claws（爪子）. There are two main types of sloths. You can tell them apart by the number of their claws. Sloths hardly move. They spend most of their time sleeping in the trees.

    But now, with the increase of population, human beings（人类）cause a lot of problems for these slow and quiet animals. The main problems is that the forests are becoming smaller and smaller. When trees are cut down, sloths will fall and break themselves. Sloths who live near human beings sometimes are hit by cars or attacked by dogs.

    At the centre, workers care for the injured animals. Their goal is to help the sloths return to the wild when are healthy enough.

    As space science develops, man has learned more and more about space. Space is not only amazing but also dangerous. While working in space, spacemen are facing danger.

    Scientists have found out that radiation(辐射) is the greatest danger to spacemen in space. When spacemen are working in space, they are in danger of radiation from the sun and other stars, which is bad for their health. Some special medicine may work a little, but there's no really helpful medicine.

    Space junk is also thought a great danger to spacemen. It's reported that there are 9,000 man-made things flying in space. About 30% of these are man-made satellites(卫星),10% are spaceships, and the rest are space junk. An explosion(爆炸) in 1996 made a cloud of 300,000 fragments(碎片), each at least 4 mm in size, and even a small piece of these knocked against a spaceship window and did some damage. Scientists are working on helpful ways to do with space junk.

    Although space is really dangerous, it interests everyone on the earth. In the near future, it may become usual for people to spend a few days in a space hotel. We may even choose to leave the earth and live in space for a few years. So we should care for space and do something to help improve the space environment.