When you hear about trees cut for paper, you might think of your favorite trees in the backyard, nearby parks or wild forests being cut to pieces.

 The good news is that production and use of paper will not cause forests to disappear. Most trees used for paper come from timberlands(林地). People plant trees here for use. It usually takes 10 to 20 years for trees to grow big enough to be cut down. During that time, trees provide a home for animals and produce oxygen(氧气) for the earth. And after people cut down the big trees, they plant small ones again.

 Often, a tree is not cut down for making paper at all. People use the big part for buildings. Paper is then made from the left small part.

 We also recycle paper—People collect used paper and turn it into new products, likes boxes, newsprint and writing paper, in the factory. So it's important for us to recycle paper and reduce(减少) the amount(数量) of it in landfills(垃圾处理场).

    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.

    Brooke wanted a dollhouse and some sugar cookies. So the 6-year-old asked Alexa to get them. Alexa wasn't her mom or babysitter. It was a voice-activated home assistant powered by AI (人工智能). And it made Brooke's wishes come true. A few days later, much to her parents' surprise, a $170 dollhouse and four pounds of cookies showed up. They ate the cookies and gave away the dollhouse to a local hospital. And that's not the end of the story. When a news reporter told the story of what happened on TV, Alexa devices (设备) in many listeners' homes woke up and tried to order dollhouses!

    Alexa isn't the only AI willing to serve you. Apple Home Pod has Siri, Google Home has its Assistant, and the upcoming Galaxy Home device will have Bixby. People who have these devices use them mainly for listening to music, checking the weather, and setting timers. According to a report from The Information, nowadays voice shopping is rare. But many scientists predict a boom (增长) in voice shopping in the near future. Is that a good thing?

      ▲   You can shout out an order as soon as you think of it, even if you are cooking, cleaning, or driving. In addition, people with disabilities who are unable to use a keyboard or mouse can shop without any help.

    But voice shopping has its disadvantages. Unwanted dollhouses aren't the biggest problem. It's usually very easy to cancel an order or return products. The thing that worries some people is that these assistants are always listening. They have to be able to respond when you want them. So they listen for "Alexa" or "OK Google" or another order. When they hear it, they start recording the conversation. Some have worried about what happens shopping habits? And what if someone hacks (入侵) the device? The CIA found a way to hack smart TVs to turn them into spies that listen all the time. Others could do the same with any smart device.

    What do you think? Are you ready to start voice shopping?

Popsicles

Popsicles were invented by 11-year-old Frank Epperson in 1905. He forgot a drink of juice and left it with a stir（搅拌） stick in it outside on a cold night. The next day it was ice. Because of this he couldn't drink it any more, but he could eat it. It tasted good! These ice sticks became popular among kids at school in summer because they were delicious and helped them stay cool.

More than a hundred years later, popsicles are sill one of the best summer treats!

Crayon Holdans

When 11-year-old Cssidss Coldstein needed crayons for a school project, she had a hard time because, there were so many small or broken ones. She found some small clear plastic tubes（管子）at home. Although the tiny tube were usually filled with water to keep flowers fresh, she found that they fit tightly （紧紧地） around the crayons. She was now able to hold them easily. This is how she invented Caryon Holders.

Wristies

When snow gets in kids' gloves and their hands get wet, they feel uncomfortable. 10﹣year﹣old Kathryn Gregoary decided to do something about it. She created the wristies as she wanted to keep her wrists（手腕）warm and dry. Wristies are long gloves with no fingers and they are worn under your coat. They help you when you work in the cold because your hands stay warm while you use your fingers. With her parents' help, Kathryn also opened a small shop where she sold her wristie. And she still runs it today.

All these inventions have one thing in common—the kids were trying to solve problems in their lives. When you meet problems, what would you do？ If the kids can do it , you can do it, too!

Liu Yaxuan is totally a homebody. Every weekend, this 14-year-old student from Tsinghua High School watches popular TV dramas and plays with her mobile phone. She hates playing outdoor sports."It's too tiring,"she said.

She is not alone. In recent years, more and more Chinese teenagers are becoming homebodies. A 2013 survey of kids aged 2 to 14 showed about half of them spend less than one hour doing outdoor activities every day.

To some extent, heavy academic pressure (学业压力) caused this situation. Hu Huilan, 12, from Shenzhen Nanshan Language School, is busy with piles of homework and extra classes on weekends."I don't want to get behind,"she said.

Even if this isn't a problem, kids still prefer indoor life. Wang Yidi, 12, from Anhui No. 50 Middle School, often reads Harry Potter, listens to music and surfs the Internet at home."I can do so many things I like at home rather than hang out in smoggy weather,"she said.

But this causes bad health conditions. Chinese teenagers' physical conditions have been dropping for about 28 years, reported a newspaper last year.

The situation for teenagers should be changed. They should spend their free time outdoors even if it just means going to the park or reading a book under the tree. Nice weather, little homework and rich outdoor activities enable them to do that. It helps them stay energetic.

 You are walking down the street. Suddenly it starts to rain and you don't have an umbrella. What do you do? Run or walk?

 Most people would rather run because it will get you out of the rain faster. But if you run, you also run into more raindrops. So, what should you do?

 Things are more complicated(复杂的) than you might think. Franco Bocci, a professor at the University of Brescia in Italy, found that whether you should travel slowly or quickly in the rain depends on the wind direction and your body shape, according to the BBC

 When there is no wind, and the rain lands directly on you, Bocci suggests that you should run and hide as fast as possible. But if the wind comes from behind and blows the rain onto your back, the best thing to do is to walk at the same speed as the wind. This way , both your front and back will stay mostly dry.

 This is not all. When the wind blows in from the side, you' ll have to think about one more thing— your body shape. Thinner people are hit by fewer raindrops. In this case, a fatter person had better run while a thinner person should still try to match their speed to the wind.

" In general, the best thing is to run, as fast as you can- not always, but in general ." Bocci told BBC News," If you' re really thin, it's more probable that there will be a best speed. Otherwise , it is better to run fast."

Now you know what to do next time the rain catches you in the middle of the street. But the best way to stay dry is still to carry an umbrella.