Every animal sleeps,but the reason for this has remained foggy. When lab rats are not allowed to sleep, they die within a month.{#blank#}1{#/blank#} 

    One idea is that sleep helps us strengthen new memories. {#blank#}2{#/blank#} We  know that, while awake,fresh memories are recorded by reinforcing (加强)connections between brain cells, but the  memory processes that take place while we sleep  have been unclear.

    Support is growing for a theory that sleep evolved so that connections between neurons(神经元)in the brain can be weakened overnight, making room for fresh memories to form the next day.  {#blank#}3{#/blank#}

    Now we have the most direct evidence yet that he is right. {#blank#}4{#/blank#} The synapses in the mice taken at the end of a period of sleep were 18 per cent smaller than those taken before sleep,showing that the connections between neurons weaken while sleeping.

If Tononi's theory is right, it would explain why, when we miss a night's, we find it harder the next day to concentrate and learn new information —our brains may have smaller room for new experiences.

    Their research also suggests how we may build lasting memories over time even though the synapscs become thinner. The team discovered that some synapses seem to be protected and stayed the same size. {#blank#}5{#/blank#}  “You keep what matters,” Tononi says.

    Do you want to learn a new language?{#blank#}1{#/blank#}Do you need it for a practical reason,such as your job or your studies?Or perhaps you're interested in the literature,films or music of a different country.{#blank#}2{#/blank#}

    Most people learn a language best by using a variety of methods.However,traditional classes are an ideal start for many people.They provide an environment where you can practice under the guidance of someone who's good at the language.We all lead busy lives and learning a language takes time.{#blank#}3{#/blank#}As a result,you should try to develop a routine.It doesn't matter if you haven't got a long time.Becoming fluent in a language will take years,but learning to get by takes a lot less.

    Many people start learning a language and soon give up.“I'm too old,” they say.Yes,children do learn languages more quickly than adults.{#blank#}4{#/blank#}And learning is good for the health of your brain,too.I've also heard people worry about the mistakes they make when learning.Well,relax and laugh about your mistakes.I'm sure you're much less likely to make them again.

    {#blank#}5{#/blank#}But with some work and devotion,you'll make progress.And you'll be amazed by the positive reaction of some people when you say just a few words in their own language.Good luck!

A.Learning a new language is never easy.

B.The very first thing to think about is why.

C.You must inspire your kids to learn it well.

D.You will have more success if you study regularly.

E.Maybe you know the language will help your work a lot.

F.Sometimes you have to quit it because of too much work.

G.But research has shown that you can learn a language at any age.

Read the following passage and then answer the questions.

    When thinking back to an experience that has affected me the most, I can't help but recall the first time I performed for a crowd with my band.

    As I stood in the dark, in front of 300 people, my head began to pound and my eyes began to hurt from straining to see the faces before me. No matter how many times I wiped off my hands, they were covered with sweat, making them fumble across the strings of my guitar. Then, in a flash, the spotlights were turned on and the crowd yelled. My heart raced and I knew that the night of my first concert would be exciting and memorable.

    The concert was held annually at Frank's school. Being the largest activity for the students in the spring, we were told to expect the whole school to come to see us play. That fact went over and over in my mind. True, I had played in the school band in concerts for many people, but that was with a large group and I had sat in the back. Here it was just the three of us, all up front. I had had different visions of what performing would be like, but what ended up happening was a pleasant surprise.

    During the first song, the crowd stood in a mixed state of confusion and excitement. I could see nothing but their dark shapes, some swaying to the beat of the bass drum, others standing still, examining our every move. The song ended with hesitant applause.

    Glancing at Frank, the guitarist and singer, I read a message in his eyes. "I don't think they like us." His look pierced through my heart and I almost left the stage, yet kept going anyway. The second and third songs went the same way with the crowd looking at us like monkeys in a zoo. But then the magic started.

    Our fourth song we had was written for the occasion and it was as if it were the beginning of a trip that we would take with the crowd of onlookers. The funk bass and driving drums seemed to pick these people up like puppets and do with them what they pleased. The crowd danced and jumped and clapped, in and out of beat. Our music was giving these people a reason to lose their inhibitions and for a short time, enjoy themselves. By the end of the second to last song the crowd was at our mercy. Finally creating a situation that I had only dreamed of, during the last song the crowd began to sing the words. But it was not just any song, it was a song we had written. This sent my heart racing and I couldn't help smiling and even laughing. The song ended and an echoing roar came over the crowd.

    The concert was to me part of a childhood dream. My friends and I were responsible for giving 300 people a good time for an evening. They sang my words and they hummed my tune, and all helped to make the dream come true. That night back in my room, I sat up all night. I saw the bodies dancing in front of me and heard their screams. Even though I may perform in college and in the future, this feeling is one I may never feel again.

The Cost of Thinking

    Despite their many differences, all human beings share several defining characteristics, such as large brains and the ability to walk upright on two legs.

    The first unique human characteristic is that humans have extraordinarily large brains compared with other animals. It seems obvious that evolution should select for larger brains. Mammals (哺乳动物) weighing sixty kilograms have an average brain size of 200 cm². Modern man has a brain averaging 1200-1400 cm². We are so fond of our high intelligence that we assume that when it comes to brain power, more must be better. Unfortunately, that is not the case.

    The fact is that a huge brain is a huge drain—consumption of energy—on the body. I's not easy to carry around, especially when boxed inside a massive skull (倾骨). It's even harder to provides energy. In modern man, the brain accounts for about 2-3%of total body weight but it consumes 25% of the body's energy when the body is at rest. By comparison, the brains of apes (类人猿) require only 8%of rest-time energy. Early humans pad for their large brains in two ways. Firstly, they spent more time in search food. Secondly, their muscles grew smaller and weaker. It's hardly an obvious conclusion that this is a good way to survive. A chimpanzee (黑猩猩) can't win an argument with a modern man, but it can tear the man apart like a rag doll.

    Another unique human characteristic is that we walk upright. Standing up, it's easier to find food or enemies. In addition, their arms that are unnecessary for moving around are freed for other purposes, like throwing stones or signaling. As a result, humans can perform very complex tasks with their hands.

    Yet walking upright has its disadvantage. The bone structure of our ancestors developed for millions of years to support a creature that walked on all fours and has a relatively small head. Adjusting to an upright position was quite a challenge, especially when the bones had to support an extra-large skull. Humankind paid for its broad vision and skillful hands backaches and painful necks.

    We assume that a large brain makes huge advantages. It seems obvious that these have made humankind the most powerful animal on earth. But humans enjoyed all of these advantages for a full 2 million years during which they remained weak and marginal creature. Thus humans who lived a million years ago, despite their big brains and sharp stone tools, lived in constant fear of meat-eating animals.

Is Cash Becoming Outdated?

    When he rolls into a gas station to fill his tank, Barkhad Dahir doesn't get out of his car. He pushes a few buttons on his cellphone and within seconds he has paid for the fuel. With the same quick pushes on his phone, he pays for virtually everything he needs: groceries at the supermarket, a few oranges from a market stall, or a cup of sweet milky tea from a café. Mr. Dahir boasts, "Even lying in bed, you can be paying your bills."

    Electronic payments offer consumers convenience, provide revenue for banks, credit card companies and payment processors, and offer merchants improved cash flow and convenience. "I don't even carry money any more," says Adan Abokor, a democracy activist. "I haven't seen cash for a long time. Almost every merchant, even hawker (小贩) on the street, accepts payment by cellphone. There's no waiting for it and no counting of cash."

    The system is impressively simple and secure. Purchases are made by dialing a three-digit number, entering a four-digit PIN, and then entering the retailer's payment number and the amount of money. Both customers and merchants receive text messages to confirm the payment.

    Clearing up cash payments has several advantages as well. The printing and handling of money is expensive. Cash payments can be anonymous and hard to track criminal activities to be conducted in secret. Many governments favor reducing cash dealings in order to better monitor and understand the activities of their citizens. The Swedish government has been discussing the removing of cash since 2010.

    However, some people doubt what members of a cashless society do when the power goes off. Do they choose to barter (物物交换) and rob? Do they sit at home and wait? What happens to people who rely on their cellphones to process money dealings when cell service and the Internet are interrupted? A world affected by terrorism and increasingly violent weather may not yet be ready to abandon currency. "Ironically, the day after the largest bank in Norway, DNB, proposed ending all cash dealings, I went to my local grocery store and when I tried to pay by phone, I was told that I needed to go to the ATM to get cash because the system was broken." said an interviewee.

    Other people fear that electronic payments may create security and fraud risks and enable dealings to be tracked and reported. Privacy, security and convenience are all important factors in the adoption of electronic payment technology. New technologies which balance and address these factors may enable people to remove cash.