The best-known (最熟知的) vegetable in the world is the potato. It grows in many places and does not need rich soil(土壤) like many other crops. But until four hundred years ago, the Europeans(欧洲人) began to know the potato. But today it's one of the main foods in Europe(欧洲). About half of the world's potatoes are grown in Europe.

    In France the potato was not grown for a long time .Here is story about Louis. In 1778 he saw some potato flowers for the first time .He liked them so much that he picked one and put it in his buttonhole. He was interested in the flowers not the potatoes themselves.

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    Google and Toyota have worked together to create a new smart car. It can run on the road without a driver. It drives itself. The self-driving car hasn't been on sale to the public, so we don't know how much it costs. Another thing most people want to know is whether it will be safe enough to run on the road.

The self-driving car uses electricity (电) as its power, and it can't drive very quickly—the top speed would be 25 miles per hour. It is actually controlled by a computer system on the car. The system keeps on collecting information by some video cameras inside the car and a LIDAR sensor(激光达传器) on top of it. A computer processes the information and decides what to do. "The self'-driving car has only buttons (按钮) for go and stop, so it's very easy to use," an engineer of Google says. "And what's more, it will make car accidents fewer and make the world a safer place." The self-driving car has driven hundreds of thousands of miles in California, and it has only gotten into two accidents by human mistake.

    According to CNN, self-driving cars will also help to reduce the number of cars in big cities. "Self'-driving cars would be able to send you to the workplace and then pick up another person instead of stopping in a parking lot."

    The Internet joins millions of computers all over the world,and today it is used by people all over the world.It was invented in the 1960s in the USA.The American government needed a network of computers for its army.Then in the 1970s scientists and business people also wanted to use the Internet to send and receive messages.For some years,they weren't allowed to use the US network,and when they were allowed to,the messages were in very simple text without photos.

    The World Wide Web was invented by a British scientist named Tim Berners-Lee in 1989.He wanted to send documents to other scientists,so he developed the World Wide Web.This allowed him to send and receive scientific documents with text,drawings and photos(also called multimedia documents).In the 1990s,more and more people began to use the Internet and the World Wide Web.

    So what's the difference between the Internet and the World Wide Web?The Internet is the hardware.It allows us to communicate with other people.The World Wide Web is the software.It allows us to create, see and read multimedia documents.

    The Web is made up of millions of documents called Web pages.These pages are held in computers all over the world.Many people have a favorite website with a number of Web pages on the same subject.

    The email is a way of using your computer to send and receive messages.It's cheaper and quicker to use emails than send normal mails.New users call the normal mail “snail mail” because it's too slow.It took 50 years for 100 million people to listen to the radio.It took 15 years for 100 million people to watch television.By the year 2000, it had taken only about three years for 100 million people to use the Internet.What will happen next on the Internet?

    Some animals sleep during the wintertime because the weather can be very cold and it is difficult for them to find food. They can sleep for a long time. This kind of winter sleep is called “hibernation”.

    If an animal moves about a lot, it needs food. Hibernating animals do not need to eat much because they are not moving about. Their hearts(心脏) beat very slowly and they also breathe(呼吸) slowly. They find a place that is sheltered(遮蔽的) from bad weather and where they are out of danger. Their body fat(脂肪) keeps them alive and warm.

    Some animals, such as bears, may wake up from their hibernation on warm winter days and then quickly go back to sleep again when they see the snow is still thick on the ground. When the weather becomes warmer in spring, the animals start to wake up and look for food.

    In today's world, almost everyone knows that air pollution and water pollution are harmful to people. However, not all the persons know that noise is also a kind of pollution, and that is harmful to human, too.

    People who work and live under noisy conditions usually become deaf(聋的). Today, however, scientists believe that 10 percent (百分比) of workers in Britain are being deafened by the noise where they work. Many of the workers who print newspapers and books, and who weave(织) cloth become deaf. Quite a few people living near airports also become deaf. Recently(近来) it was discovered that many teenagers in America could hear no better than 65-year-old people, for these young people like to listen to "pop" music and most of "pop" music is a kind of noise. Besides(除此之外), noise produced by jet planes or machines will make people's life difficult and unpleasant, or even make people ill or even drive them mad.

    Nowadays the government in many countries have made laws to reduce or control(控制) noise and make it less than 85 decibels(分贝).  In China, the people's government is trying to solve not only air and water pollution problems but also noise pollution problem.

    What is the most stressful (有压力的) thing in school? It is probably exams. Exams can put us under a lot of stress. But some students do better under stress, while others do not. So, why do some students behave better under stress?

    It all comes down to dopamine (多巴胺). Dopamine is a chemical in our body that sends signals in the brain. It has many important roles: influencing memory, attention and how we learn.

    Our brains work best when there is a balance (平衡) of dopamine—not too much or too little. Our brains control dopamine in two ways. It either takes out dopamine quickly, or bit by bit. Exam success can be connected to how fast dopamine goes back to a balance, according to new research from the University of Missouri, reported Yahoo.

    What happens when we take an exam? If you become stressed, your brain will start to overload on dopamine. It is like a cup overflowing with water. The quicker you are able to go back to a balance of dopamine, the quicker you can focus, helping you do better on a test.

    Scientists found that, during a test, people who slowly got back to a balance of dopamine scored 8 percent lower. That's the difference between a good mark and a bad mark.

    But don't fear, there is good news for every student. The study also found that the more practice you get, the less stressed you will be. So, it turns out that     .