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.

    People have understood that kindness is good for the person who receives help. For example, when we give food to a hungry person, he is lucky. However, scientists have recently begun to study the effect(影响)of the kindness on the person giving it. What they have found is that doing good is good for the doer(行为者).Acts of kindness can improve health, help a person reach goals and even add years to a person's life.

    The first study to show the connection between doing good and living a long life was a study on aging(衰老). Beginning in 1956, scientists studied a group of married mothers for 30 years. They thought the women with the most children would die first. But the number of children a woman had did not matter. Wealth did not matter. Education did not matter. What did matter was whether they volunteered. Women that volunteered had fewer diseases during their life.

    Many other studies have found the same positive(积极的)effects. Helping other people improves long-term health. The gains are the same for men, women, old people and the young. Those who volunteered had fewer serious diseases than those who did not volunteer. This included diseases such as heart attack, cancer and stroke.

    Scientists are studying many possible causes. One possible cause is an increase in antibodies(抗体)，which help fight against disease. One study showed the body produces more antibodies after an act of kindness.

    Another one is an increase in Oxytocin(催生素)，it is a chemical that fights the effects of stress from life. Scientists have found a link between being kind to people and an increase in the chemical oxytocin.

    China has recently published its first artificial intelligence(AI,人工智能) textbook for high school students in Shanghai to start AI lessons. Forty high schools around the country have become experimental bases for exploring AI education.

    The book, Fundamentals of Artificial Intelligence, includes the history of AI and how the technology can be used in areas such as facial recognition, public security and auto driving.

    Peng Yu is a teacher at the High School Affiliated(附属)to Shanghai Jiao Tong University. He took part in editing the textbook and said it would give guide to students. He said," The book has a good introduction to the area so that students can decide if they want to further study AI at college Students can also find out what they need to learn if they are interested in studying AI. For example, they have to learn Maths because it is the fundamental basis of AI."

    Peng said AI has improved the interest of many high school students already, but he still feels that they can learn much more by taking part in project—based learning programs. Peng is sure that everyone should learn some basic knowledge about AI because it will be part of our everyday lives. It is reported that China needs 5 million AI teachers to keep up with development in the future.

    Have you noticed the waste bins(垃圾桶) in different colors on the street? Do you often put all the waste in the same bin? It's reported by Changchun Daily that people must do waste sorting(分类)in most places in Changchun at the end of 2019. Waste sorting is a wonderful way to make good use of energy and protect the environment. But do you know how to sort the waste?

    Usually, people should sort their waste into four groups: wet, recyclable, harmful and dry. Different kinds of waste should go into different bins. Wet waste means the things you don't want but pigs can eat, mostly coming from your kitchen. Things that can be used again, such as paper, metal and glass, are recyclable waste. Harmful waste might be dangerous or cause serious pollution, like medicine and batteries(电池). And any waste that's not wet, recyclable or harmful will go into the dry waste bin.

    Different countries are trying different methods to sort the waste. A university in England has invented a smart bin. When people drop their waste into the bin. It can tell what kind of waste it it and sort it correctly. The bin can also compress the waste to make it smaller in size and take up less space. In South Korea, people have to separate their food waste from other kinds of waste and pay for it. The more food waste they throw away, the more they pay. Japan has the strictest rules for waste sorting in the world. For example, plastic bottles and their caps should go into different bins.