Some of the world's most significant problems never hit headlines. One example comes from agriculture. Food riots（暴动）and hunger make news. But the trend lying behind these matters is rarely talked about. This is the decrease in the growth in production of some of the world's major crops. A new study by the University of Minnesota and McGill University in Montreal looks at where, and how far, this decline is occurring.

    The authors take a vast number of data points for the four most important crops: rice, wheat, corn and soyabeans. They find that on between 24% and 39% of all harvested areas, the improvement inproduction that took place before the 1980s slowed down in the 1990s and 2000s.

    There are two worrying features of the slowdown. One is that it has been particularly sharp in the world's most populous countries, India and China. Their ability to feed themselves has been an important source of relative stability both within the countries and on world food markets. That self-sufficiency (自给自足) cannot be taken for granted if productions continue to slow down.

    Second, production growth has been lower in wheat and rice than in corn and soyabeans. This is problematic because wheat and rice are more important as foods, accounting for around half of all calories consumed. Corn and soyabeans are more important as feed grains. The authors note that "we have preferentially focused our crop improvement efforts on feeding animals and cars rather than on crops that feed people and are the basis of food security in much of the world."

    The report also states the more optimistic findings of another new paper which suggests that the world will not have to dig up a lot more land for farming in order to feed 9 billion people in 2050, as the Food and Agriculture Organisation has argued.

    Instead, it says, thanks to slowing population growth, land currently ploughed（犁）up for crops might be able to revert (回返) to forest or wilderness. This could happen. The trouble is that the prediction assumes continued improvements in productions, which may not actually happen.

    Many years later, when people recall the 2018 Russia World Cup, they will remember many things. With the tragic ending of the defending champion Germany, Mexico has triumphantly and suddenly lost three goals in the face of Sweden. But people will never forget the back of a lonely person. That is Lionel Messi.

    31-year-old Messi took off the green armband of his left arm and suddenly fell out. In the recent match, he and his team lost the game against France. The 19-year-old striker Mbappé relentlessly ripped apart the Argentine defense line and scored twice, which made a great contribution to the victory of France.

    On this planet, anyone who knows a little about football knows the name Lionel Messi and his golden years from 2007 to 2017.

    In 2007, 19-year-old Messi tied Real Madrid three times with a hat-trick, and began his legendary career.

    In the past ten years, Mr. Football, the Golden Globe Award and the Golden Boot Award have been taken over by him.

    He led Argentina and Barcelona to make a name for themselves in the world, and has a brilliant record in the Champions League, America's Cup and World Cup.

    Eleven years later, Messi stood on the Kazan Stadium. After four World Cups, he knew that this might be the last time he led Argentina to the World Cup.

    Since 1986, Argentina has never won a championship again. As a captain, he has a great responsibility, even stating that he would withdraw from the national team if he did not win the championship this year.

    This is a prophecy.

    Messi, who eventually failed to save the game, did not receive any interview after standing up on the lawn; leave behind only a legendary image for the world.

    In the United States, when one becomes rich, he wants people to know it. And even if he does not become very rich, he wants people to think that he is. That is what "keeping up with the Joneses" is about. It is the story of someone who tried to look as rich as his neighbors.

    The expression was first used in 1913 by a young American called Arthur Momand. He told this story about himself. He began earning $ 125 a week at the age of 23. That was a lot of money in those days. He got married and moved with his wife to a very wealthy neighborhood. When he saw that rich people rode horses, Momand went horseback riding every day. When he saw that rich people had servants. Momand and his wife also hired a servant and gave big parties for their new neighbors.

    It was like a race, but one could never finish this race because one was always trying to keep up. The race ended for Momand and his wife when they could no longer pay for their new way of life. They had to move back to an apartment in New York City. Momand looked around him and noticed that many people do things just to keep up with rich lifestyle of their neighbors. He saw the funny side of it and started to write a series of short stories. He called it "Keeping up with the Joneses" because "Jones" is a very common name in the United States. "Keeping up with the Joneses" came to mean keeping up with rich lifestyle of the people around you. Momand's series appeared in different newspapers across the country for over 28 years.

    People never seem to get tired of keeping up with the Joneses. And there are "Joneses" in every city of the world. But one must get tired of trying to keep up with the Joneses because no matter what one does, Mr. Jones always seems to be ahead.

    There are some very good things about open education. This way of teaching allows the students to grow as people, and to develop their own interests in many subjects. Open education allows students to be responsible for their own education, as they are responsible for what they do in life. Some students do badly in a traditional classroom. The open classroom may allow them to enjoy learning. Some students will be happier in an open education school. They will not have to worry about grades or rules. For students who worry about these things a lot, it is a good idea to be in an open classroom.

    But many students will not do well in an open classroom. For some students, there are too few rules. These students will do little in school. They will not make good use of open education. Because open education is so different from traditional education, these students may have a problem getting used to making so many choices. For many students it is important to have some rules in the classroom. They worry about the rules even when there are no rules. Even a few rules will help this kind of students. The last point about open education is that some traditional teachers do not like it. Many teachers do not believe in open education. Teachers who want to have an open classroom may have many problems at their schools.

    You now know what open education is. Some of its good points and bad points have been explained. You may have your own opinion about open education. The writer thinks that open education is a good idea, but only in theory. In actual fact, it may not work very well in a real class or school. The writer believes that most students, but of course not all students, want some structure in their classes. They want and need to have rules. In some cases, they must be made to study some subjects. Many students are pleased to find subjects they have to study interesting. They would not study those subjects if they did not have to.

    When I was five or six years old, I remember watching TV and seeing other children suffer in other parts of the world. I would say to myself," When I grow up, when I can get rich, I will save kids all over the world."

    At 17, I started my career here in America, and by the age of 18, I started my first charity( 慈善) organization. I went on to team up with other organizations in the following years, and met, helped, and even lost some of the most beautiful souls, from six-year-old Jasmina Anema who passed away in 2010 from leukemia(白血病), and whose story inspired thousands to volunteer as donors, to my grandmother, who lost her battle with cancer in 2012, and her death is the very reason and the driving force behind the Clara Lionel Foundation(CLF). We're all human. And we all just want a chance: a chance at life, a chance in education, a chance at a future, really. And at CLF, our mission is to impact as many lives as possible, but it starts with just one.

    People make it seem too hard to do charity work. The truth is, you don't have to be rich to help others. You don't need to be famous. You don't even have to be college educated. But it starts with your neighbor, the person right next to you, the person sitting next to you in class，the kid down the block in your neighborhood. You just do whatever you can to help in any way that you can. And today, I want to challenge each of you to make a decision to help one person, one organization, one situation that touches your heart. My grandmother always used to say. "If you've got a dollar, there's plenty to share."

    Researchers at the University of Chicago have trained an artificial intelligence system, to write fake reviews on Yelp, a website showing customers reviews on shopping or something else, and it's pretty hard to tell them apart from a human review.

    Their study, which will be presented at the ACM Conference on Computer and Communications Security in October, aimed to throw attention onto how easily these systems can write reviews like humans and how damaging they can become if they're not monitored properly.

    Since many small businesses rely on online reviews to help grow and keep their reputation, a future where someone—like a rival or angry customer—could crazily fill their page with negative reviews written by a machine is pretty worrying.

    And, according to the research team, the threat goes far beyond a bunch of fake reviews on Yelp. "In general the threat is bigger," Ben Y. Zhao, one of the authors of the study, said. "I think the threat towards society is large and it really misleads users and shakes our belief in what is real and what is not. I think that's going to be even unimaginable."

    To test how believable these reviews came across, the researchers invited 40 volunteers and had AI generate five fake reviews for 40 actual restaurants. The volunteers were asked how useful they thought the review was and whether or not they thought it was fake. The AI reviews ranked as "effectively indistinguishable" from real reviews，according to the study. Further, the fake reviews were given a 3.15 "usefulness" rating, compared to a 3.28 rating for human reviews.