Language students often think they have memory problems. They worry because they can't remember words. In fact, the problem usually isn't with their memory. The problem is with how they study.

    To remember words better, you need to understand how memory works. There are two kinds of memories: short-term and long-term. When you see, hear, or read something, it goes first into short-term memory. But short-term memory lasts for only a few seconds. You will only remember something longer if it goes into long-term memory. Your long-term memory is like a very big library with many, many books. And like a library, it's organized (有条理的). When you put away a book – or memory – you can't just leave it anywhere. You have to choose a place where you can find it again.

    How can you do this with vocabulary? The answer is to work with the word and think about the word in new ways. You can do this by writing new sentences that include it. Even better, you can invent a little story about the word, with people or places that you know. Another way is to make a picture in your mind with the word. For example, if the word is height, you can think of the tallest person you know and try to guess his or her height. All of these activities are good ways to think about words. They make the meaning of words stronger in your long-term memory. And they give a way to find a word when you need it.

    Every object has weight. But the center of its weight is not always in the middle of the object. If the top of an object is heavier than its bottom, it will fall over easily. We say that its center of gravity is high. But if the bottom is heavier, it won't fall easily. Then we say that its center of gravity is low.
    Look at the first picture. This empty box must fall over, because its center of gravity (C) is not above the line of its bottom (AB).
Now look at the second picture. There is some heavy iron in the bottom of this box. It will not fall, because its center of gravity is above its bottom.

    In most parts of the world, many students help their schools make less pollution. They join environment clubs. In an environment club, people work together to make our environment clean.

    Here are some things students often do.

    No-garbage lunches. How many lunch bags do you throw away after lunch? Environment clubs ask students to bring their lunches in bags that can be used again. Every week they will choose the classes that make the least garbage and report them to the whole school.

    No-car day. On a no-car day, nobody comes to school in a car including the students and the teachers. Cars give pollution to us, so remember：

    Walk, jump, bike, or run!

    Use your legs! It's lots of fun!

    Turn off the water! Do you know that some toilets can waste twenty to forty cubic meters of water an hour? In a year, that would fill in a small river. In the environment clubs, students mend those broken toilets.

    We love our environment. Let's work together to make it better.

    AI (人工智能) makes our lives easier and better. Let's see the amazing AI.

     Xinhua News Agency reported 3,000 yellow school buses started their service in Chongqing1the end of 2011. These school buses are like the ones in the US as we usually see on TV and in 2 .

    The school buses are bright yellow in colour. They are 3than the army's cars. They are from the US. The yellow school bus has a big 4.This keeps the students safe when other cars crash into the school bus. The bus also has some   5devices(设备), such as warning lights and a stop signal arm.

    In China, school buses became popular in the past few years. On the bus, except(除了) the bus driver, there is always a 6whose duty is to watch the students. Children usually rest on the bus. Some of them also recite texts. School buses in China are not 7.The fee is different from school to school.