Monarch butterflies from eastern Canada make the most amazing journey in the insect world. Each year, this butterfly travels about 3000miles to its winter home in central Mexico(墨西哥). How can it fly so far? And why does it make this long and dangerous trip? Scientists still don't have an answer.

 For many years, people in Mexico wondered where the orange-and-black butterflies came from every winter. Then, in 1937, a scientist started to follow and study the butterflies. For the next 20 years, he discovered that one butterfly started its journey in Canada. Four months later, it arrived in Mexico.

 The length of the butterflies find their way back to the same place? Another amazing thing is that the butterflies always return to the same area in central Mexico.

 How do the butterflies find their way back to the same place? This is an interesting question because only every fourth generation(代) makes the trip south. In other words, the butterfly that travels to Mexico this year is the great-great-grandchild of the butterfly that traveled there last year.

 Each year, four generations of a Monarch butterfly family are born. Each generation of the family has a very different life. The first generation is born in the south in late April. It slowly moves north, reproduces(繁衍), and then dies. On the trip north,two more generations are born, reproduce, and die. Each of these generations of butterflies is born. This generation has a much longer life. It lives for about eight months. This generation of butterflies makes the amazing journey back to the winter home of its great-great-grandparents. The butterflies spend the winter there, and in the spring they reproduce and then die. Their offspring will be the first generation of the next circle of life.

 Today, people are still studying the Monarch butterfly. But they are not clear about everything.

    Ladies and gentlemen, I returned to this year in a time machine. In the year 2500, we are able to travel through time to any year in the history of the earth. This year is your last chance to change your lifestyle to save the earth.

    Beginning in the middle of the 20th century, a few people were worried about polluting the earth's water and air, but most people did not change their way of life.  Instead, they continued to pour(倒) dangerous chemicals and other waste into lakes and seas, to drive more and more cars and trucks, and to cut down trees.

By the year 2200, the earth's water was completely polluted. Scientists said that in the future there might be too many people on the earth. People could no longer drink water, and they had to use other types of liquids(液体).

So, by the year 2300, there were so many people that food became scarce. There was no water to grow food and all of the fish in the lakes and seas died because of pollution Terrier wars(战争) broke out between the rich and the poor. Scientists were working very hard to find another planet in space where humans could live on.

By the year 2400, the air was too polluted for humans to breathe. So we had to leave earth but only the rich were able to leave. Where did we go? Nowhere. And everywhere. You see scientists did not find another safe planet, so now we must travel around the universe in our space ships. We are still looking for a place to call our home.

    So, it is up to you to change history. There is still hope. You must change your lifestyle now, before it is too late.

    You don't need to get in a time-travelling machine to see how technology will change our lives, such as the way we shop. Several new technologies that are to change your buying habits already appear. Let's see what's in store for your future shopping.

    Try it on, virtually(虚拟地). Want to shop online for a new pair of glasses? You don't need to guess which pair looks best on you—use the eBay Fashion iPhone app to try a pair of glasses you're checking out on a picture of your face. But what about buying something bigger? Thanks to Microsoft Kinect's action tracking(跟踪)camera, you can cover clothes on your screen body. You can even choose the background of your virtual fitting room to improve your shopping experience.

    Get a perfect, custom fit. Everyone's body is shaped differently. To get a perfect fit, you sometimes have to get your clothes changed. But by using 3D scanning technology, all the clothes you buy will fit your body perfectly. Some companies scan(扫描)your body using High-tech to get the real sizes, so they can make special clothes just for you.

    High-tech shopping carts(推车)and checkout counters(收银台). High-tech shopping carts could be common in malls and supermarkets in the future. Microsoft Kinect-enabled carts are under test. The cart can follow you along the aisles(通道), controlled only by your movement and your voice.

    In the United States, several supermarkets use a certain set called "Scan It" that gives buyers the freedom to scan products on their own while they shop. If we don't want to wait in line before the checkout counters, we can use Toshiba's new object Recognition Scanner. The machine identifies(辨认)a product as soon as it's placed in front of a camera just by its shape and color, even if it has no bar code.

    Cars make our lives more convenient. But they can also be a problem. For example, fossil fuel(化石燃料) cars mainly cause air pollution.

    To improve the environment, many countries are developing electric vehicles (EVs,电动车). Among them, China is taking a leading role and has created the world's largest EV market.

    Last year, over 40 percent of the 753,000 EVs sold in the world were sold in China, more than twice as many as the number sold in the United States.

    "Filling up a fossil fuel car with gas(汽油) is more expensive than charging( 充电) an electric car，" said Wu Hao，who bought an electric car this year.

    However, there are still some problems. It can be hard to find charging piles(充电桩) and the cars can't go far before needing to be recharged.

    Some of these problems are being solved. In 2014，China had 31,000 charging piles. Now China has the world's largest EV charging network, with more than 167, 000 charging piles in total.

    Developing EVs is one of many efforts that China has made to cut down pressure on its environment after the government promised to stop increases in carbon dioxide emissions(二氧化碳排放量) by 2030.

    "As China goes, so will the world's car industry," The Wall Street Journal said. China has taken a leading role in the world's electric vehicle industry.