I want to tell you the story of one of my old friends called Bob，His teachers called him A Troublemaker，They also said that he had no future and no hope. But now he owns a small second -hand bookstore store which makes him enough money to live on and also to support his mother.

    He told me that after he finished grade nine, he went to study at a technical college. He was a pretty bad student so he became one of the gang (一帮) leaders there. Many of them got caught many times for fighting.

    It looked like nothing could change his life. That was until one sad day when his father died. That changed everything.

    After his father died, his mother had to work very hard to make enough money to support the family. He told me that he really pitied his mum after his dad died. He felt that he needed to earn some money rather than let his mum work alone. He loved reading cartoon(卡通)books and had been collecting them for years. As his family was short of money, he decided that he should sell them. He did this by the side of the road where his mother was selling food.

    Soon he realized that his books were very popular. So he decided to set up his own business. He started his business by going around buying cartoon books from other people. He bought them for 25% and then sold them for half price. He could make enough money to help support the family.

    He was a troublemaker to his teachers but he is a hero to me. If you are judged as a bad student or as someone being stupid, I suggest you pay no attention to what they say. Just do your best in everything. Don't give up so easily. Believe in yourself. If you think that you can do it, then you can. Believe me, one day you could be more successful than those persons who looked down upon you.

    The year is 2094. It has been announced that a comet (彗星) is heading towards the Earth. Most of it will miss our planet, but two pieces will probably hit the southern half of the Earth.

    On 17 July, a piece four kilometers wide enters the Earth's atmosphere with a massive explosion. About half of the piece is destroyed, but the remaining part hits the South Atlantic at 200 times the speed of sound. The sea boils and a huge hole is made in the sea bed.  Huge waves are created and spread outwards from the hole. The wall of water, a kilometer high, rushes towards southern Africa at 800 kilometers an hour. Cities on the African coast are totally destroyed and millions of people are drowned.

    Before the waves reach South America, the second piece of the comet lands in Argentina. Earthquakes and volcanoes are set off in the Andes Mountains. The shock waves move north into California and all around the Pacific Ocean. The cities of Los Angeles, San Francisco and Tokyo are completely destroyed by earthquakes. Millions of people in the southern half of the earth are already dead, but the north won't escape for long. Because of the explosions, the sun is hidden by clouds of dust, temperatures around the world fall to almost zero. Crops are ruined. The sun won't be seen again for many years. Wars break out as countries fight for food. A year later, no more than 10 million people remain alive.

    Could it really happen? In fact, it has already happened more than once in the history of the Earth. The dinosaurs were on the Earth for over 160 million years. Then 65 million years ago they suddenly disappeared. Many scientists believe that the Earth was hit by a piece of object in space. The dinosaurs couldn't live through the cold climate that followed and they died out. Will we meet the same end?

    A young woman carrying a three-year-old child got on a bus. The conductor hurried to give her a warm welcome and then kindly asked the other passengers to make more room for the woman and her child. On seeing this, people were surprised and began to talk. "You know this conductor used to be very rude. Now suddenly he has changed his bad behavior, "said a middle-aged man.

    "Yes, he should be praised and we must write a letter to the company," said a second passenger. "That's right," another lady said, "I wish a newspaper reporter were here so that more people could learn from this conductor.”

    Just then a gentleman who looked like a teacher turned to the conductor and said, "Excuse me, but can I know your name, please? Your excellent service must be praised."

    Before he could open his mouth, the three-year-old child sitting on the young woman's lap interrupted, "I know his name. I call him Dad."

    If a diver surfaces too quickly, he may suffer the bends. Nitrogen(氮) dissolved(溶解) in his blood is suddenly liberated by the reduction of pressure. The consequence, if the bubbles (气泡)accumulate in a joint, is sharp pain and a bent body—thus the name. If the bubbles form in his lungs or his brain, the consequence can be death.

    Other air-breathing animals also suffer this decompression(减压) sickness if they surface too fast: whales, for example. And so, long ago, did ichthyosaurs. That these ancient sea animals got the bends can be seen from their bones. If bubbles of nitrogen form inside the bone they can cut off its blood supply. This kills the cells in the bone, and consequently weakens it, sometimes to the point of collapse. Fossil (化石)bones that have caved in on themselves are thus a sign that the animal once had the bends.

    Bruce Rothschild of the University of Kansas knew all this when he began a study of ichthyosaur bones to find out how widespread the problem was in the past. What he particularly wanted to investigate was how ichthyosaurs adapted to the problem of decompression over the 150 million years. To this end, he and his colleagues traveled the world's natural-history museums, looking at hundreds of ichthyosaurs from the Triassic period and from the later Jurassic and Cretaceous periods.

    When he started, he assumed that signs of the bends would be rarer in younger fossils, reflecting their gradual evolution of measures to deal with decompression. Instead, he was astonished to discover the opposite. More than 15% of Jurassic and Cretaceous ichthyosaurs had suffered the bends before they died, but not a single Triassic specimen(标本) showed evidence of that sort of injury.

    If ichthyosaurs did evolve an anti-decompression means, they clearly did so quickly—and, most strangely, they lost it afterwards. But that is not what Dr Rothschild thinks happened. He suspects it was evolution in other animals that caused the change.

    Whales that suffer the bends often do so because they have surfaced to escape a predator (捕食动物) such as a large shark. One of the features of Jurassic oceans was an abundance of large sharks and crocodiles, both of which were fond of ichthyosaur lunches. Triassic oceans, by contrast, were mercifully shark- and crocodile-free. In the Triassic, then, ichthyosaurs were top of the food chain. In the Jurassic and Cretaceous, they were prey(猎物) as well as predator—and often had to make a speedy exit as a result.

    Have you ever heard of agritourism where you can experience farm life? If not, Dr. Cindy Ayers-Elliott will tell you the real story of Foot Print Farms.

    The original concept of building Foot Print Farms was simple. When Ayers-Elliott returned to her hometown after graduation, she didn't have to look any further than her state's alarming health statistics to find a mission. Everywhere she turned, there were reports of high blood pressure, diabetes, obesity and heart disease. "The problem was already identified." explains Ayers-Elliott. "Too many Mississippians were seriously unhealthy and it didn't take research to see that. And many of the state's greatest health challenges could directly result from poor diet. "

    These days, Foot Print Farms, which started with a few raised beds of herbs and vegetables, is making fresh, naturally grown food. "When speaking of the key to my success, the co-op model works because we share the work and rewards," notes Ayers-Elliott. "A perfect example is the Wingfield High School football team. To earn the money for equipment and other items, players committed to working five hours a week on the farm, and by the end of the summer they had produced 1, 000 melons and the profits from their sales helped to buy weights, T-shirts, sweat suits and pregame meals. But the lessons they learned about the rewards of hard work and working together to accomplish something were even more valuable products of their efforts."

    "It' s a model that can easily be learned in other places and I' m looking forward to seeing some of our current partners do just that——to take what they have learned here and spin it off in other communities," Ayers-Elliott remarks. She is now looking forward to developing an agritourism aspect to the farm, where visitors can experience farm life, learn new skills and take with them seeds of inspiration they can sow in their own communities when they return home.

    Last week, Vodafone started a test of the UK's first full 5G service, available for use by businesses in Salford. It is part of its plan to trial the technology in seven UK cities. But what can we expect from the next generation of mobile technology?

    One thing we will see in the preparation for the test is lots of tricks with the new tech. Earlier this year, operators paid almost £ 1.4 billion for the 5G wavelengths, and to compensate for that cash, they will need to catch the eye of consumers. In September, Vodafone used its bit of the range to display the UK's first hologram (全息) call. The Manchester City captain Steph Houghton appeared as a hologram in Newbury. It isn't all holograms, however: 5G will offer faster internet access, with Ofcom (英国通讯管理局) suggesting that video that takes a minute to download on 4G will be available in just a second.

    The wider application is to support connected equipment on the "internet of things" -not just the internet-enabled fridge that can reorder your milk for you, but the network that will enable driverless cars and delivery drones (无人机) to communicate with each other.

    Prof William Webb has warned that the technology could be a case of the emperor's new clothes. Much of the speed increase, he claims, could have been achieved by putting more money in the 4G network, rather than a new technology. Other different voices have suggested that a focus on rolling out wider rural broadband access and addressing current network coverage would be more beneficial to the UK as a whole.

    Obviously, 5G will also bring a cost to consumers. It requires a handset for both 5G and 4G, and the first 5G-enabled smart phones are expected in the coming year. With the slow pace of network rollout so far, it is likely that consumers will end up upgrading to a new 5 G phone well before 5 G becomes widely available in the next couple of years.