A recent study found people's lives are made shorter in North China. It is showed the life expectancy(平均寿命) had been cut down by 5.5 years there. Researchers（研究者）think that the heavy air pollution in China should be to blame(承担责任). It's really the truth. Our government has already done something. However, it doesn't seem to work so well.

    “Air pollution in China is doing harm to people's health. The harm is much more serious than we can imagine,” said Chen Yuyu of Beijing University, one of researchers of this study.

    Dirty air brings serious problems in North China. In January this year, the air pollution was worse than that in other places. That was caused by rising temperature and waste gas（气体）from coal heating（燃煤）.

    Chinese government should strongly fight with air pollution. They should think of more proper ways to deal with the problem. People should be encouraged to take buses, ride bicycles or walk, instead of driving cars. The factories that pollute heavily should be closed.

    “We need to improve our environment, although it might be expensive. Protecting our environment means protecting ourselves,” Li Hongbin, another researcher of the study said.

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    Artificial intelligence（人工智能）, or AI in short, is the science of giving computers and machines ability to think and work like humans. AI scientists and engineers have made a lot of cool technologies.

    AI is rapidly catching up with the human ability to read faces. As a result, facial recognition（识别）is used a lot in the world. Chinese police use this technology to identify criminals（罪犯）.Once they caught a criminal when he attended a concert. It also checks the ID of ride-hailing（网约车）drivers and lets people pay for things with a smile.

    AI is also used in self-driving cars, which are believed to be the future of driving. Most drivers may wave or nod at passers-by to let them cross the street, but self-driving cars don't have this ability. Carmakers are testing a light signal system to help them "speak" to humans. The system can show what self-driving cars will do. For example, if a driverless car is yielding（让路）, it will flash two white lights side to side. A rapidly flashing light tells passers-by that the car is about to speed up.

    Service Robots also show you know powerful AI is. Imagine this—you come back home from school and your robot housekeeper is waiting for you at the door. After dinner, he teaches you to play the piano, just like a real music teacher. Such thoughts will soon happen in the real world. In the future, more and more service robots will become good home helpers.

    AI is so powerful that it can help human beings and even replace us in many jobs.

    There's much to see under the sea, but you need to remember that light behave differently in water than in air. The objects appear closer to you than they exactly are. You might find yourself reaching out to touch something and completely missing it.

    Objects under water will appear larger than they would on the surface, too. Be careful not to tell any stories about the big fish that got away. That fish might not be so big after all! It's just because sometimes things can seem to be as much as about 33 percent bigger in water!

    What's more, in deeper water, colors just don't seem as bright. In fact, it looks as if some colors are missing. Remember the color of an object results from the wavelength (波长) of light that are reflected (反射) from its surface. And light is taken in as it moves down through the water.

    Swimmers wear wet suits to keep warm underwater. Let's take a bright red, yellow, and blue wet suit as an example. These colors are hard to miss on the surface of water. Watch carefully the changes in color as you descend in the water. The red part now looks almost black because the red light wavelengths, the longest among these three colors, are missing. As you go down deeper, the same thing will happen to the yellow part and in the end to the blue part. Even at a place of about 6 to 9 meters underwater, you will look terrible, like a ghost(鬼怪) ! And you have to wait for your return to the surface to enjoy the bright colors again!

    Why is music so important to children? Here are some of my thoughts on the subject.

    Music has a positive（积极的） effect on young children's development!

    New research shows that music has a good influence on young children's cognitive（认知的） skills, such as spatial reasoning（空间推理） and memory. Research also shows that offering children an interesting environment can support children's healthy growth and development.

    Young children enjoy making music with others!

    Making music with others gives children a wonderful feeling of belonging to the group. Children might have difficulty joining in activities with others because they are shy, have limited language ability or special needs, but they can freely take part in a music activity.

    Music makes young children happy!

    Children seem to experience much pleasure and joy when listening to music, making music and dancing to music. Whether they are singing along to a CD, playing an instrument or dancing to music around the classroom, most children seem to thoroughly（彻底地） enjoy participating in a music activity. How wonderful it is to offer children the chance to do some activities about music!