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.

    There are many kinds of food in the world. Scientists know a lot about them. They say that there are some kinds of food people must eat every day. For example, people must eat some green and yellow vegetables. We shouldn't eat too much meat. People also need to eat some fruits, bread and rice. Of course our bodies need some water and milk.

    Scientists say people in different countries and different places eat different kinds of food. They cook food in different ways. Different people eat at different times. In one place, people eat once or twice a day. But in another place, people eat three or four times. The scientists say when to eat and how many times to eat are not important. What we eat is the most important thing.

    Nowadays, the world faces two problems. People in some places, for example, in Africa, are not full. Many people are eating junk food. It's bad for people's health. So it's our duty to make everyone full and make everyone healthy.

    Rainforests (热带雨林) cover six percent of the earth's surface (表面). There are rainforests in many parts of the world. About 75 percent of animals live in rainforests. There are many beautiful birds, insects and so on. Some of them live on the ground, some live under the ground and others live in the trees, over 30 meters from the ground. It is always hot in the rainforests and the ground is always wet. It is also very dark there.

    The rainforests are very important for us. We need them! The trees and other plants in the forest help to make the air clean. They also help to control (控制) the temperature.

    Unfortunately, in many places, the rainforests are in danger. For example, many years ago there was a large rainforest in Java, but now there is nothing. The same thing happens now in many other parts of the world. It's time to take action to save the rainforests. We can never imagine a world without rainforests. If rainforests disappeared from the earth, we wouldn't find any trees, flowers or fruits. What's more, we wouldn't get clean air, and we wouldn't find any animals. The worst result would be that we wouldn't find any humans.

    You don't need to get in a time-travelling machine to see how technology will change our lives, such as the way we shop. Several new technologies that are to change your buying habits already appear. Let's see what's in store for your future shopping.

    Try it on, virtually(虚拟地). Want to shop online for a new pair of glasses? You don't need to guess which pair looks best on you—use the eBay Fashion iPhone app to try a pair of glasses you're checking out on a picture of your face. But what about buying something bigger? Thanks to Microsoft Kinect's action tracking(跟踪)camera, you can cover clothes on your screen body. You can even choose the background of your virtual fitting room to improve your shopping experience.

    Get a perfect, custom fit. Everyone's body is shaped differently. To get a perfect fit, you sometimes have to get your clothes changed. But by using 3D scanning technology, all the clothes you buy will fit your body perfectly. Some companies scan(扫描)your body using High-tech to get the real sizes, so they can make special clothes just for you.

    High-tech shopping carts(推车)and checkout counters(收银台). High-tech shopping carts could be common in malls and supermarkets in the future. Microsoft Kinect-enabled carts are under test. The cart can follow you along the aisles(通道), controlled only by your movement and your voice.

    In the United States, several supermarkets use a certain set called "Scan It" that gives buyers the freedom to scan products on their own while they shop. If we don't want to wait in line before the checkout counters, we can use Toshiba's new object Recognition Scanner. The machine identifies(辨认)a product as soon as it's placed in front of a camera just by its shape and color, even if it has no bar code.

    Do you believe that only boys do well in science? Does it seem that girls have better language skills than boys? In your opinion, are boys better at building things? If your answer to each of those questions is" Yes", you are right, according to an article in Current Science. There are exceptions(例外),but here are the facts.

    Usually, boys score higher in tests about math, while girls do better in tests about words, spelling and memory. But these differences may not always be true. In the future, a person's abilities may not be decided by sex. As one scientist says, "Nothing is impossible for a person to be or do."

    A recent study by Jerome Kagan, a scientist at Harvard University is studying the watching ability of children who are 10 months old. Baby boys and baby girls are watching "show" while seated on their mothers' laps. In Act One of the show, an orange-colored ball is lifted from a blue box and moved slowly. Then it is returned to the box. This is repeated six times. Act Six is almost the same, except that the orange ball is smaller. Baby boys do not seem to notice the difference in the size of the ball, but girls immediately become excited and begin to make noises that sound like language.

    It's also known that baby girls usually talk at an earlier age than baby boys do. Scientists believe that the left side of the brain develops faster in girls than in boys. As a result, by the time they start to go to school, little girls have an advantage that boys don't have, but what have the boys been doing in the years before starting school? They have been developing something called aggression. An aggressive person feels strong and independent. He is often the first one to start a fight. It is said that aggression is caused by hormones(荷尔蒙). Scientists believe that hormones are not the only cause. They say aggression in boys is also caused by mothers.