Recent research from the Pew Internet Project suggests that 90% of Americans aged from 12 to 17 use the Internet, and 51% of those teens use social networks. However, there are many possible problems with social networking sites and the teenagers who use them.

Apart from the social advantages, social networking sites can be used to record school research, develop artistic talents and experiment with other forms of subject creation. They provide a way to communicate with others who share the same interests and to get helpful advice on ongoing projects.
Along with these advantages come some dangers. For example, most social networking sites are open to all, especially MySpace, which is the most popular social network among teens in America. It means that they could be put in unpleasant and frightening situations.
A greater danger is that teens may become objects of the people with secret purposes. The secrecy of some social networking sites makes it easy for dangerous people to find young teens and invite them into dangerous conversations. It's easy for them to pretend as teens and draw children into dangerous real-world communication as well. Then further hurt might be on its way.
Another danger is identity stealing, which can happen when teens share too much information about their names, dates of birth and locations.
Therefore, it's very important to make sure teens are safe when they use social networks.
Many of the same rules that work for online chat work for these sites:
※Don't use your real name.
※ Don't give out personal information to people you don't know. A last name and a town are enough for a bad guy to find where you are.
※ Don't believe that people are who they say to be.
※ Immediately end any communication that makes you uncomfortable and report it to a parent.
Only if you are sure of your safety, can you enjoy the fun brought by social networking. Besides, trying to deal with all problems on your own can lead to terrible results. Remember, asking your parents or school officials for help doesn't mean you are unable to do anything but wiser than many others.

    The kangaroo is the world's largest living marsupial (有袋动物). It was first found on the island of southwestern Australia. The animal was given its name by a famous English tourist in the 18th century.

    The kangaroo may be 7 feet(2.1m) tall when standing upright and the male can weigh as heavy as 200 pounds(90kg). The female (雌性) is smaller and lighter than the male. The kangaroo's head is small, but its ears are large, and its fore feet are really small. The animal has strong back legs and long tail.

    The kangaroo usually covers from 5 to 10 feet(1.5 to 3m) with each jump. The female is usually faster than the male. The mother kangaroo has a pouch (育儿袋) in its abdomen (腹部). The baby kangaroo grows up in the mother's pouch slowly.

    The kangaroo lives on grass and other plants. It is always moving from one place to another, lying down to sleep on the ground during the night. It likes to enjoy the warm sunshine. When it's in danger, it can use its back legs and strong tail to protect itself.

    Answer the following questions with No more than 6 words.

    Today, many endangered animals live in zoos. There, scientists work to keep each species(物种) alive. How do they do that? One way is by taking cells(细胞) from animals. Then the cells are frozen(冷冻). They can be used in the future to help animals reproduce.

    The San Diego Zoo has been freezing cells for 40 years. It's also called the Frozen Zoo. Now, the zoo is the biggest of its kind, with a large gene bank. It has cells from more than 1,000 species. One of the species is the northern white rhinoceros(犀牛).

    There are only five northern white rhinoceros alive in the world now. They are unable to have their children. Some scientists there want to use the bank's frozen cells to produce another northern white rhinoceros. They want to do this before the species dies out. That could happen by 2025.

    Can the zoo save the northern white rhinoceros? Other species have been saved successfully. So it's possible for the white rhinoceros too.

    Saving the white rhinoceros would be expensive. So some people don't think using frozen cells is the best thing to do. Some wonder whether it's worth spending millions of dollars on the species that nearly dies out. Some say scientists should work on the reasons why animals become endangered in the first place.

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My name is Maisie Hall and I have five brothers and sisters! Life in our house is fun, but it's difficult, too.

On school days I get up very early at 6:30 a.m. I have my breakfast first. After breakfast I take a shower and get dressed.

At 8:00 a.m. we go to school by bus. School starts at 8:30 a.m. and we go home at 3:00 p.m. After school I don't watch TV. I clean the house for my mom and play with my brothers and sisters.

We have dinner together at 7:00 p.m. My baby brother goes to bed at 8:00 p.m. and my other brothers and sisters go to bed at 9:00 p.m. Then I can study!

From 9:00 p.m. to 10:00 p.m. I do my homework and read a book. After that I brush my teeth and go to bed.