Do you know why different animals or pests have their special colors? Colors in them seem to be mainly used to protect themselves.

Some birds like eating locusts (蝗虫), but birds cannot easily catch them. Why? It is because locusts change their colors with the change of the colors of crops. When crops are green, locusts look green. But as the harvest time comes, locusts change into the same brown color as crops have. Some other pests whose colors are different form plants are easily found and eaten by others. So they have to hide themselves for lives and appear only at night.

    If you study the animals' life, you'll find the main use of colors is to protect themselves. Bears, lions and other animals move quietly through forests. They cannot be easily seen by hunters because their colors are much like the trees.

    Colors are useful not only on the land, but also in the sea. A kind of fish in the sea can give out a kind of black liquid (液体) when the fish face danger. The liquid spreads over quickly, so they cannot be found by their enemies and can quickly swim away. That is why they live safely though they are not strong at all.

    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?

    Three powerful ocean storms hit the Caribbean, the coast of the southeastern United States and southeastern Mexico. They come as the state of Texas recovers from Hurricane Harvey (飓风哈维). The huge storm caused serious flooding and billions of dollars in damage in Houston, the country's fourth-largest city.

    Hurricane season in the Atlantic Ocean goes from June 1 to November 30. And most storm activities happen in me month of September.

    Hurricanes are the most powerful storms in the Earth's atmosphere. The storms have different names depending on where they take place. Scientists call all these storm tropical cyclones (热带气旋).

    If the storms form over the Atlantic Ocean or eastern Pacific Ocean, they are called hurricanes. Storms that form in the western Pacific Ocean are known as typhoons. In the Indian Ocean, they are called cyclones. Although they have different names, all these storms form in the same way.

    Scientists at the American space agency NASA describe tropical cyclones as huge weather "engines" that use warm, moist (潮湿的) air as fuel.

    They can only form over warm, tropical waters near the equator (赤道).

    A tropical cyclone develops when warm moist air near the surface of me ocean rises. This creates an area of unusually low air pressure.

    Higher-pressure air from surrounding areas pushes in to take the place of the warm, rising air. It becomes warmer and moister and rises, too.

    The rising, moist air goes high into the atmosphere, where temperatures are low. This creates wind. The moisture forms clouds. The developing weather system begins to spin because of the Earth's rotation (旋转).

    As the storm spins faster and faster, an "eye" of the storm develops at its centre. This is a calm area of very low pressure. Higher pressure air from above flows down into the eye.

    Technology is developing fast and it has become an important part of our life. Then what will the world be like in the future?

    3—D food will be both delicious and nutritious(有营养的). We can use 3—D printers to print some basic materials.    ①    And we can go further. Scientists belive that we just need to turn on a printer in the kitchen and then we can enjoy our favourite food whenever we like.

         ②      5G network will allow many more people to get information. Big companies like China Mobile and China Unicom will start to offer 5G. It is said that promises download speeds 10 to 20 times faster than 4G. For example, we can download a film within just 1 second. But with a 4G network, it takes a few minutes. There will be much bandwidth (带宽) and we can get unlimited (无限的) information.

    Underwater cities will provide more space. The earth is becoming more and more crowded. We may turn to underwater homes, which will be built as low as 15 of the sea can be used to provide power for the homes.

         ③      For us common people on the earth, the dream of travelling around space will come true. In the coming years, spacecraft will be as popular as buses, trains and planes. We can leave our home and enter space to take an adventure (冒险). And even we will get used to living there.

    A robot will be a part of life.  Robots can do many of the same things as we humans do like driving cars. But they will be used in other areas as well. They will be able to think. They can tell the difference between right and wrong. They can feel       ④        In a word, just as Jules Verne said, "Anything one man can imagine, other men can make real."

    After years of research and testing, the hybrid car was developed and put on the market. It's an interesting and exciting new improvement in today's world as we look for better ways to protect the quality of the air we breathe and save our natural resources.

    The quality of our air is affected by many different things. But one of the largest sources of air pollution is the burning of fossil fuels such as coal and gasoline which is used to power a car's engine. The EPA has set national standards to help control the level of harmful pollutants sent off into the air, and the automobile industry has acted by producing a hybrid car that uses less gas and therefore causes less pollution.

    A hybrid car is a combination of a regular car that runs on gasoline and an electric car that is battery powered. Some people tend to think that since the hybrid car is partially electric, you have to plug it in to charge it. But that's not how it works. The 144 volt battery pack is actually recharged through the energy that is produced when the car's brakes are used. This is referred to as "regenerative braking", because it produces electricity.

    Although the hybrid car still runs on gasoline most of the time, this helps it use less gas than a regular car. When the driver stops at a traffic light, the engine automatically shuts off to save fuel. Then, as soon as the driver puts the car in gear and touches the gas pedal, the engine starts back up.

    Have you ever ridden in a car with someone who ran out of gas? That probably wouldn't happen if you were riding in a hybrid car. It flashes a warning on its computer screen that says, "I am low on gas". When it completely runs out, the warning reads, "YOU ARE NOW OUT OF GAS!" Then the electric power supply kicks in to let the driver travel a few more miles to a gas station.