A group of students at Sunshine School are holding a charity sale to raise money to help their classmate Lisa. Lisa had cerebral palsy (大脑性瘫痪) when she was a baby. People who have cerebral palsy have trouble walking. Although Lisa has to use a wheelchair (轮椅) to help her get around, she never gives up.

    "Lisa has the chance of standing up, but she needs an operation (手术)," Lisa's doctor said.

    "I never thought that I could stand up one day. Actually the news is surprising for me. However, when I see my parents are worried about the cost of the operation, I am sad. I don't mind if I can't stand up," Lisa said. "Now my classmates and some other kind people are helping me. I am really thankful."

    "While helping Lisa, we can also learn a lot. We have learned how to cook cookies (曲奇饼) and how to sell them," Betty, one of Lisa's classmates said. "Now we know making money is not easy, so we won't waste money anymore."

    Alex, a boy in Lisa's class, told a reporter that they could raise about $100 every day. "We have raised about $2,100 so far. We hope we will raise more money for Lisa's operation," he said.

A

    The founder of Apple Steve Jobs was one of the fathers of the personal computing time. Here are some of his greatest inventions.

    Professor Xu Yuanchong was born in 1921. He is best known for translating (翻译) Chinese ancient poems into English and French. Xu took foreign language studies at Tsinghua University and then he studied abroad. After that, he became a professor in English and French.

    During these years, he has been working on translating. Up to now, he has translated more than 100 Chinese classics from Chinese to both English and French. The first poem he translated from Chinese to English is Don't Cast Away in 1939. It's a poem written by Lin Huiyin. In fact, he translated this poem to express his love to a girl he liked. Though he failed, he got a life-time career in translation.

    In 2007, Xu had a cancer. During the time, he did what he liked every day and didn't give up translating. What's more, he didn't go to sleep till three or four o'clock in the morning. He still held on to work over twelve ours a day. Also, he became the first Asian to win the"Aurora Borealis"Prize.

 "Have you ever heard that it's impossible to fold a piece of paper more than seven times? Actually, it is just a popular myth. 

The myth refers to folding a piece of paper in half many times in any direction. The paper is folded in half. Try it for yourself with a piece of notebook paper. ____ But when you make the fifth and sixth folds, you'll notice that it's increasingly hard to fold the paper. Why does it happen? Because the number of the layers (层) of paper doubles with each fold. For example, after the sixth fold, you're left with 64 layers of paper. If you have strong hands, you may be able to make that seventh fold. If you start with a piece of paper that is 0.01 centimeters thick, it'll be as thick as a notebook after seven folds. And it would seem impossible to make more folds. At this point, you may be thinking that the paper-folding myth doesn't sound much like a myth.

However, in 2002, a high school student named Britney Gallivan proved the idea wrong. Britney successfully folded a 1.20-meter-long roll of toilet paper 12 times (note that she used single-direction folding). She also developed a math rule. This is convenient. It allows you to find out the maximum (最大的) number of possible folds based on paper thickness, paper length, and direction of folding.

Since Britney's success, many people have managed to fold a single piece of paper more than 7 times. Students even folded a piece of toilet paper a total of thirteen times. The toilet paper they used was about 4,000 meters long!

Christopher's mother now is sitting proudly and watching TV as Christopher is given the "Child of Courage" prize by his favorite TV star. This makes her remember the accident happened to them. 

Christopher was sitting in the car with his mother, father, sister Rosie, 10, and brother Mac, 7, when his father drove onto a metal barrier(障碍物). Unluckily, the car fell down from a hill into a deep river. Christopher, then 12, swam through a broken window and got out for the fresh air. Then he realized his brother and sister were still in the car. 

Christopher took a deep breath and swam back into the car. He saved Mac first, then he swam back to look for Rosie, who was under the cold, dark water, in the car. Christopher had to feel for her seatbelt because he couldn't see anything in the water. He took the seatbelt off her, and went up for air. Finally he went back to pull her out of the car. 

Christopher's mother and father were thrown out before the car rolled down the hill. When his mother came back to her life, she looked for her children hurriedly. She could see Mac on the bank, but she couldn't find the other ones. She was so worried. Then she saw Christopher come up out of the water like a dolphin with Rosie on his shoulder. She shouted excitedly to Christopher down to the river, "I'm so proud of you. "

The family called for an ambulance (救护车). It took Christopher's father who was badly hurt to a nearby hospital immediately. 

 The concept of dynamic pricing is simple— and easy for businesses to implement. Whether it's a Friday-evening fight, a hotel during the holidays, or a taxi ride in a storm, we have all been burned by higher-than-normal prices due to excess demand. Raising costs when businesses are busiest is the norm(常态) across the travel industry. Perhaps the most well-known example of this is within ride-share companies, which have used surge pricing(峰时定价) for years to charge riders when demand for cars increases rapidly compared to the number of drivers available.

 Outside travel, online stores are increasingly using this dynamic pricing, too, says Vomberg. "On Amazon.com alone, millions of price changes occur within a day, corresponding to (对应于) a price change of about every ten minutes for each product." While consumers might not always pick up on these little changes in price, Vomberg says time-based dynamic pricing will likely become a competitive standard at least in online markets. "AI-enabled tools can suggest the best prices via machine learning algorithms(算法). They can also track and learn competitor and customer responses to price changes," he says.

 Now, surge pricing is happening in stores including bars and supermarkets as well. "Physical businesses are adopting electronic shelf labels that enable real time price adjustment depending on the time of day, stock levels and whether items are approaching their sell-by date," says Sarwar Khawaja, chairman of the Oxford Education Group. He says this technology is likely to cause prices in bars that use these signs to increase during the rushes of dinner, weekends or holidays, or for supermarkets to adjust prices throughout the day or week, depending on the number of shoppers.

 The current economic climate is also driving the need for these pricing technologies. While creating competitive prices is always key to healthy profit margins(利润率), Khawaia says dynamic pricing enables businesses to optimize (使优化) their pricing depending on the financial situations of their customer base. "Businesses can offer discounts during downturns while increasing prices in better off areas," he says.

 The changes, however, may not sit well with consumers. "Dynamic and surge pricing will likely expand to more industries and more companies in the long term, but just because a product may be popular does not mean that customers are willing to turn a blind eye to being charged more," says Khawaja. He adds surge pricing can cause customers to lose faith in a company if they believe they are being overcharged. "Perhaps dynamic pricing of a drink in your favourite pub might be a step too far for loyal customers."