These days, many students like playing 3D games. Do you know what 3D games are like? In most 3D games, game players need to control (控制) a character. The character can be a robot or a soldier (士兵). Game players usually use the mouse to make the character move around in his own world. Game players can find things such as food and weapons (武器) to help them go on with the game. The character can go straight, sit down, turn left, turn right or pick up things in the game.

    Some 3D games have many levels (等级). The character needs to finish different goals for each level. Game players can play against their computers, and sometimes they can play with other players on-line. It's great fun to play 3D games. But playing 3D games for long is not good for our study.

    Twinkle, Twinkle Little Star is a lovely song for children, but it has two misunderstandings (误解). First, stars aren't little. Some may be Earth-sized, but most are bigger than Jupiter, the largest planet in the solar system (太阳系). Second, they don't twinkle; they shine. And the brightness and color of the light from each star provide information about its temperature, size and even its age. viewing the stars from Earth is a bit like looking at them through a water filter (过滤器) because the air is thick compared to the emptiness of space. What is more, air is always moving, so starlight appears to be moving, too. The air also makes stars appear dimmer (暗淡的) than they would be if we could see them from space.

    If you stop and look at the sky carefully on a dark and moonless night, it's easy to find color differences among stars. The color of a star is a signal of its surface temperature. The hottest stars are blue, and the next hottest are white. Yellow stars like the sun are next, while red stars are the coolest of the visible (可见的) stars. Many red stars are so dim that people can't see them at all, and some stars hardly send out any light at all. One reason that stars different in brightness is that hotter stars produce more energy than cooler ones, but another important reason is that some are much bigger than others.

Some stars appear brighter to humans simply because they're closer. Astronomers rank (排列) the brightness of stars which are seen from Earth by giving them a name known as magnitude (光度) —the smaller the magnitude, the brighter the object. They have also designed a number that ranks stars according to how bright they are when compared to each other. With a magnitude of minus 26.7, the sun is the brightest object in the sky.

    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.

    ●No-garbage lunches. How much 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 the no-car day, nobody comes to school by car—not the students or not the teachers! Cars give pollution to the air, so remember:

    Walk, jump, bike or run.

    Use your legs! It's lots of fun!

    ●Turn off the water! Did you know that some toilets can waste twenty to forty liters (升) of water an hour? In a year that would fill a small river! In environment clubs, students mend those broken toilets.

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

    We all know that many inventions have changed our life a lot. They play important roles in our daily life. Here are some interesting inventions.