One day, Mr. Arnold was teaching a lesson, and things were going as normally as ever. He was explaining the story of human being to his pupils. He told them that, in the beginning, men were nomads (游牧); they never stayed in the same place for very long. Instead, they would travel about, here and there, in search of food, wherever it was to be found. And when the food ran out, they would move off somewhere else.

    He taught them about the invention of farming and keeping animals. This was an important discovery, because by learning to cultivate (耕作) the land, and care for animals, mankind would always have food steadily. It also meant that people could remain living in one place, and this made it easier to set about tasks that would take a long while to finish, like building towns, cities, and all that were in them. All the children were listening attracted by this story, until Lucy jumped up:

    “And if that was so important and improved everything so much, why are we nomads all over again, Mr. Arnold?”

    Mr. Arnold didn't know what to say. Lucy was a very clever girl. He knew that she lived with her parents in a house, so she must know that her family were not nomads; so what did she mean?

    “We have all become nomads again,” continued Lucy, “The other day, outside the city, they were cutting the forest down. A while ago a fisherman told me how they fish. It's the same with everyone: when there's no more forest left the foresters go elsewhere, and when the fish run out the fishermen move on. That's what the nomads did, isn't it?

    The teacher nodded, thoughtfully. Really, Lucy was right. Mankind had turned into nomads. Instead of looking after the land in a way that we could be sure it would keep supplying our needs, we kept developing it until the land was bare. And then off we would go to the next place! The class spent the rest of the afternoon talking about what they could do to show how to be more civilized (文明的).

    The next day everyone attended class wearing a green T-shirt, with a message that said “I am not a nomad!”

    And, from then on, they set about showing that indeed they were not. Every time they knew they needed something, they made sure that they would get it using care and control. If they needed wood or paper, they would make sure that they got the recycled kind. They ordered their fish from fish farms, making sure that the fish they received were not too young and too small. They only used animals that were well cared for, and brought up on farms.

    And so, from their little town, those children managed to give up being nomads again, just as prehistoric men had done, so many thousands of years ago.

    We've all experienced that feeling that comes when your phone makes a sound to tell you that its battery level is low. It often comes at the worst times – when you're out on a trip and don't have a charger, or when you're expecting an important phone call.

    Indeed, this feeling is so common that South Korean electronics manufacturer LG has given it a name: low battery anxiety.

    According to a survey of 2,000 US adults conducted by the company last year, 90 percent of respondents said that they panic if their battery level reaches 20 percent or lower.

    And last month, UK telecommunications service provider 02 found that around 15.5 million Britons live in “constant fear” of their mobile phones running out of power, according to a survey by the company.

    “The problem is not about being unable to make calls, but is rooted in the fact that smartphones are now where we store digital memories,” noted the Daily Mail.

    However, battery worries don't just affect smartphone lovers. Many owners of electric vehicles also suffer from so-called “range anxiety”. This refers to the concern that the vehicle may not make it to its destination before the power runs out.

    Meanwhile, it isn't just low power that people worry about. A study carried out by South Korea's Sungkyunkwan University and China's City University of Hong Kong found that many of us also worry about not having constant access to our phone.

    This condition is known as nomophobia, short for “no mobile phone phobia（恐惧症）”. Symptoms include feeling uncomfortable when access to one's phone isn't possible, being unable to turn off your phone, and constantly topping up the battery to make sure it never dies.

    So, why do so many people treat their smartphone with such importance? The underlying reason may be that they keep us connected to the people around us, and if we're unable to use our phone, we feel like we're cut off from our social life.

    With products with bigger batteries being released all the time though - such as Xiaomi's Mi Max smartphone range or Tesla's Model S cars – battery anxiety may hopefully soon be a thing of the past.

    In 1858, two men wanted to be elected United States Senator from Illinois. One was Stephen Douglas. The other was Abraham Lincoln. Douglas was already the Senator, but his term in office was up. Lincoln had once been a U.S. Representative but was then a lawyer in Illinois.

    The men agreed to have seven public meetings, or debates, in seven different cities in Illinois. That way, voters all over the state would have a chance to hear what each man stood for.

    The first debate was in Ottawa on August 21, 1858. The main thing the men disagreed on was slavery. Douglas believed that as new states joined the union, they should decide for themselves whether or not they wanted to be a slave state or a free state. Lincoln believed that slavery should not spread beyond the states that already had slaves. He said the United States could not survive as half-slave and half-free states.

    The debates drew large crowds in all seven cities. People in the entire country were paying attention. Lincoln lost the Senate race. The debates did, however, make him well known everywhere.

    In 1860, it was time to elect a new President. Lincoln won the Republican party's nomination(提名). Douglas won the Democratic party's nomination. The two men again faced each other to get the people's votes. This time Lincoln won. He became the nation's 16th President.

    The slavery issue was still causing bad feelings between slave and non-slave states. By the time Lincoln took over as President on March 4, 1861, seven states had left the union. A month later, the Civil War began.

    When I was a little child, my parents divorced, making my mother a single parent. We had little money, but my mom gave me a lot of love. Each night, she sat me on her lap and spoke the words that would change my life, "Kemmons, you are certain to be a great man and you can do anything in life if you work hard enough to get it."

    At fourteen, I was hit by a car and the doctors said I would never walk again. Every day, my mother spoke to me in her gentle, loving voice, telling me that no matter what those doctors said, I could walk again if I wanted to do it badly enough. She drove that message so deep into my heart that I finally believed her. A year later, I returned to school—walking on my own!

    When the Great Depression（大萧条）occurred, my mom lost her job. Then I left school to support the family. At that moment, I was determined never to be poor again.

    My real change occurred on a vacation I took with my wife and five kids in 1951. I was angry that the second-class hotel charged an extra $2 for each child. That was too expensive for the average American family. I decided to open a motel（汽车旅馆）for families that would never charge extra for children. There were plenty of doubters at that time.

    Not surprisingly, mother was one of my strongest supporters. We experienced a lot of challenges. But with my mother's words deeply rooted in my soul, I never doubted we would succeed. Fifteen years later, we had the largest hotel system in the world—Holiday Inn. In 1979 my company had 1,759 inns in more than fifty countries with an income of $ 1 billion a year.

    You may not have started out life in the best situation. But if you can find a task in life worth working for and believe in yourself, nothing can stop you.

    It is estimated that more than half the world's population is bilingual (双语的), and in an increasingly globalised world, there are obvious benefits of speaking more than one language. However, for many years, parents were advised not to teach their children to speak more than one language from birth. Learning two or more languages simultaneously (同时) was believed to cause confusion and slow down academic development. While it is certainly true that children who are learning to speak more than one language as their mother tongue will often mix the languages up or speak a little later, these are temporary problems, and there is no reason to avoid teaching a child more than one language.

    In fact, there are plenty of reasons to encourage your child to become bilingual from birth. As well as the obvious benefits of being able to communicate with more people, and the possibility of earning more money, children who speak more than one language have been shown to score more highly in achievement tests at school. This is true for mathematics as well as tests of verbal (言语的) skills.

    And in later life it has been found that bilinguals, on average, will tend to develop Alzheimer's disease five years later than monolingual speakers. Speaking three or more languages offers even more protection. It seems that the increased number of connections within the brain allows bilinguals to cope better with brain damage.

    But is it too late if you haven't already learned a second language in childhood? It used to be thought that the adult brain was very fixed, but recent research has shown that we continue to develop new connections in the brain throughout our lives, meaning that it's perfectly possible to learn another language to a high standard. Older learners are less likely to have native-like pronunciation, but they are better at learning vocabulary as they are able to use far more skills and strategies than children. And learning a language is like using a muscle – the more you use it, the stronger it gets, meaning that you will find your third language easier than your second, and so on.

    Your next Saturday night takeaway could be brought to you by a robot after a major food delivery company announced plans to use automated vehicles to transport meals. Europe's biggest online takeaway food company Just Eat has partnered with Starship Technologies to deliver food with robots on the streets of London later this month. "Nobody has ever done deliveries with land-based robots," said Allan Martinson, the chief operating officer of Starship.

    The robot courier can travel up to 4 miles per hour for about 10 miles. It uses a GPS signal and nine cameras to navigate (确定方向). Instead of a person arriving at their door, customers could find themselves receiving a notification on their phone that says a robot is on its way and a code to unlock the automated courier. "Put the code in, the robot opens up, and there's your food," said David Buttress, chief manager of Just Eat.

    The robot, which has so far been tested in Greenwich, Milton Keynes and Glastonbury, costs £ 1 to transport within 3 miles, compared with the £3 to £6 it costs for a human courier. To date 30 robots have driven nearly 5,000 miles without getting into an accident or finding themselves picked on by passers-by. They have driven in more than 40 cities around the world, including London and Tallinn, Estonia.

    An initial worry was how the public would react to robots. But Martinson said the public has been calm when passing the delivery machine on the streets. "The most surprising reaction has been the lack of reaction," said Martinson.

    Another significant fear was that people would disrupt (扰乱) the robots, or try to steal them and their contents. To prevent this, the robot is fitted with nine cameras, two way audio, and movement sensors that send a warning if it is lifted off the ground. And it opens only with a passcode provided to the customer via a notification. "It's much easier to shoplift than it is to steal a robot," said Martinson.