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.

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    It is reported that some developed countries have shipped broken parts of computers to China. Last month Hong Kong officers found 131,000 kilograms of broken computers, TVs and phones sent from Japan.

    Things like these are called electronic waste, or e-waste. Dealing with them is not an easy job. Every time an old computer breaks down, it needs to be dealt with safely. What is worse, at present, broken computer parts are usually buried. It may be hundreds of years before they are really g one in the earth.

    Many places in China are polluted by e-waste. Guiyu in Guangdong Province is one of them. This town is named as "the e-waste capital of the world". It has to deal with 1.5 million kilograms of e-waste each year, from which it makes 75 million yuan. But it comes at a cost. Many of the poisons in e-waste find their way into the environment. An environmental group has found the air, the earth and the rivers in Guiyu badly polluted.

    Luckily, the Chinese government wants to change the situation. This year, China passed a new environmental protection law. Computer companies like Lenovo and Dell will be asked to take back their old computers. Hopefully, the problem with e-waste will be solved in the near future.

    North American black bears are shy animals. They are fearful by nature, and will usually run away if they see or hear people. Because of this, it can be difficult for scientists to learn about these animals.

    In order to study black bears, researchers from New Jersey, the US, catch bears and use drugs to help them go to sleep. Researchers then work out the size and the weight of the bears, take blood, to test for diseases, remove a tooth and take it to the lab to find out its age. From these studies, researchers want to find out how many bears live in New Jersey, how long they live, and how many babies they produce.

    But in Minnesota, the US, researchers study bears that are completely awake. The bears know the researchers' voices and they are not afraid of the research team. With the help of a few grapes to keep the bears busy, researchers can touch them to check their hearts, look at their teeth, and do other jobs. Researchers can also walk or sit with bears for hours and make videos to learn about their everyday lives."

    In both places, the main purpose is the same—to make sure there is a healthy population of black bears. But the research methods and the kinds of information that researchers are able to collect are quite different.

    If you look at the top of your phone, you'll usually see a little symbol that says 3G or 4G.The "G" stands for the "generation (代)" of your mobile phone network. But these symbols will become things of the past after 5G networks fully arrive.

    On March 30, Shanghai vice-mayor Wu Qing made the first 5G video call on a Huawei Mate X smartphone, CGTN reported. Shanghai has also become the first city in China to start testing 5G networks.

    About 100 times faster than 4G networks, 5G will let people download and upload data faster than ever before. But 5G won't just bring faster mobile Internet. People can use it to do many other things as well.

    For example, 5G will help to make self-driving cars safer. Today's self-driving test cars have one problem-lag (延迟). When the car "sees" an obstacle (障碍物), it sends he information to a data center and receives instructions. However, it takes time to send and receive the information with this kind of lag, the cars might crash because they don't receive instructions in time. With 5G, this lag will be greatly lowered, making the cars safer according to CNN.

    5G could also be used to power the Internet of Things (IoT). This means a large online network that connects all things and people. Fast Internet speeds will be the key to developing this technology. The IoT could be used in a lot of ways. For example, with IoT, your fridge could automatically (自动地) place an order online for eggs when it finds that there are no eggs left.

    Almost every Chinese can recite the famous poem, "Every grain on the plate comes from hard work(谁知盘中餐, 粒粒皆辛苦)."But sadly, many of us don't actually get the real meaning of these lines：Don't waste food.

    A CCTV programme, News One Plus One, reported that the food Chinese people throw away every year is enough to feed 200 million people for a year.

    Do we have too much food? No, according to the UN World Food Programme, there were 925 million hungry people around the world in 2010, especially in developing countries.6 million children die of hunger every year.

    Chinese people are well-known for being generous. Many even feel that they will lose face if their guests have eaten all the food on the table.

    Luckily, a number of people have realized the importance of saving food. In November, 2011, Li Hong, a waitress in a restaurant in Nanjing, became famous because she took some leftover(剩余的)food home for her son. Many people stood by her side and agreed that it was not right to waste food.

    What should we do in our daily lives to save food? Here are some tips：

    Do not order too much in a restaurant. Only order what you want to eat. If you cannot eat all the food you ordered, take the rest of it home.

    Don't be too picky(挑剔的)about food. Some food may not taste great, but your body needs it.

    Keep an eye on what food you have at home. Don't buy too much, especially vegetables and fruit.