Every day, a homeowner in Pennsylvania is reminded of a mistake he made 13 years ago. At around 8 in the evening, his peaceful house comes alive with the noise of an alarm clock he dropped into the wall over ten years ago. It's been stuck in the wall ever since.

    13 years ago, Jerry Lynn wanted to make a hole through his living room wall, so he could pass the television cable (电缆)through it. He didn't want to destroy any pipes in the wall, so he came up with a good idea to make sure that he was drilling(钻孔) in an empty place. He took his alarm clock, tied it to a string(线) and set it to go off in 10 minutes. Then he lowered it into the wall, and waited for it to ring. His goal was to drill a hole in a safe place near the place where the ringing was coming from, making sure that there was nothing to pass through there. It all went smoothly until the alarm clock fell into the wall.

The man didn't get back the alarm clock, but thought it would probably run out of battery(电池)in several months, so he wasn't too worried about it. But 13 years later, the alarm clock still rings every day.

    As you can imagine, Jerry and his wife have gotten used to the ringing living room wall, but it can still surprise  guests. So Jerry decides to pull down that wall, just to stop that boring thing, though after putting up with it for 13 years, he think it will be a pity. He says, “I've never herd of a clock battery lasting that long and my friends think it may be interesting to see how long it will keep ringing for.”

    Far out in the lake was a large wooden platform(平台) on which stood an improbably high diving board- a kind of wooden Eiffel Tower. It was, I'm sure, the county's tallest wooden structure (结构) and no one had ever been known to jump from it. So it was quite a shock when our teacher, Mr. Milton, announced that he would dive off the high board that very afternoon.

    Word of his questionable plan was already spreading through town as Mr. Milton swam out to the platform. He was just a tiny, stick figure when he got there but even from such a distance the high board seemed almost to touch the clouds. Once at the top, he paced the enormously long board , then look some deep breaths and finally stood at the edge. He was going to do it.

    Several hundred people had gathered at the shore to watch. Mr. Milton stood for quite along time ;then he raised his arms, took one bounce(弹跳) and launched himself into ;perfect dive. He fell with perfect style for what seemed minutes. The crowd fell silent. But about three quarters of the way down he seemed to have second thoughts and began suddenly to panic(惊慌)，waving his arms and legs like someone having a bad dream. When he was perhaps thirty feet above the water, he gave up on waving and spread his arms and legs wide, obviously hoping that it would somehow slow his fall. It didn't. He hit the water at over six hundred miles an hour, making birds fly out of their trees three miles away. I don't think he entered the water at all. He just bounced off it, about fifteen feet back into the air. After that, he lay still on the surface , like an autumn leaf.

    He was brought to shore by two passing fishermen in a rowboat and placed on an old blanket where he spent the rest of the afternoon. Occasionally he accepted a little water, but otherwise was too shocked to speak.

    It was the best day of my life.

C

    There's a new frontier in 3D printing that's beginning to come into focus: food. Recent development has made possible machines that print, cook, and serve foods on a mass scale. And the industry isn't stopping there.

Food production

    With a 3D printer, a cook can print complicated chocolate sculptures and beautiful pieces for decoration on a wedding cake. Not everybody can do that — it takes years of experience, but a printer makes it easy. A restaurant in Spain uses a Foodini to "re-create forms and pieces" of food that are "exactly the same," freeing cooks to complete other tasks. In another restaurant, all of the dishes and desserts it serves are 3D-printed, rather than farm to table.

Sustainability(可持续性）

    The global population is expected to grow to 9.6 billion by 2050, and some analysts estimate that food production will need to be raised by 50 percent to maintain current levels. Sustainability is becoming a necessity. 3D food printing could probably contribute to the solution. Some experts believe printers could use hydrocolloids (水解胶体) from plentiful renewables like algae(藻类) and grass to replace the familiar ingredients(烹饪原料). 3D printing can reduce fuel use and emissions. Grocery stores of the future might stock "food" that lasts years on end, freeing up shelf space and reducing transportation and storage requirements.

Nutrition

    Future 3D food printers could make processed food healthier. Hod Lipson, a professor at Columbia University, said, "Food printing could allow consumers to print food with customized nutritional content, like vitamins. So instead of eating a piece of yesterday's bread from the supermarket, you'd eat something baked just for you on demand."

Challenges

    Despite recent advancements in 3D food printing, the industry has many challenges to overcome. Currently, most ingredients must be changed to a paste(糊状物) before a printer can use them, and the printing process is quite time-consuming, because ingredients interact with each other in very complex ways. On top of that, most of the 3D food printers now are restricted to dry ingredients, because meat and milk products may easily go bad. Some experts are skeptical about 3D food printers, believing they are better suited for fast food restaurants than homes and high-end restaurants.

D

    Children as young as ten are becoming dependent on social media for their sense of self-worth, a major study warned.

    It found many youngsters(少年）now measure their status by how much public approval they get online, often through "like". Some change their behavior in real life to improve their image on the web.

    The report into youngsters aged from 8 to 12 was carried out by Children's Commissioner (专员）Anne Longfield. She said social media firms were exposing children to major emotional risks, with some youngsters starting secondary school ill-equipped to cope with the tremendous pressure they faced online.

    Some social apps were popular among the children even though they supposedly require users to be at least 13.The youngsters admitted planning trips around potential photo-opportunities and then messaging friends—and friends of friends — to demand "likes" for their online posts.

    The report found that youngsters felt their friendships could be at risk if they did not respond to social media posts quickly, and around the clock.

    Children aged 8 to 10 were "starting to feel happy" when others liked their posts. However, those in the 10 to 12 age group were "concerned with how many people like their posts", suggesting a "need" for social recognition that gets stronger the older they become.

    Miss Longfield warned that a generation of children risked growing up "worried about their appearance and image as a result of the unrealistic lifestyles they follow on platforms, and increasingly anxious about switching off due to the constant demands of social media.

    She said: "Children are using social media with family and friends and to play games when they are in primary school. But what starts as fun usage of apps turns into tremendous pressure in real social media interaction at secondary school."

    As their world expanded, she said, children compared themselves to others online in a way that was "hugely damaging in terms of their self-identity, in terms of their confidence, but also in terms of their ability to develop themselves".

    Miss Longfield added: "Then there is this push to connect—if you go offline, will you miss something, will you miss out, will you show that you don't care about those people you are following, all of those come together in a huge way at once."

    "For children it is very, very difficult to cope with emotionally." The Children's Commissioner for England's study—life in Likes—found that children as young as 8 were using social media platforms largely for play.

    However, the research—involving eight groups of 32 children aged 8 to 12—suggested that as they headed toward their teens, they became increasingly anxious online.

    By the time they started secondary school—at age 11—children were already far more aware of their image online and felt under huge pressure to ensure their posts were popular, the report found.

    However, they still did not know how to cope with mean-spirited jokes, or the sense of incompetence they might feel if they compared themselves to celebrities(名人）or more brilliant friends online. The report said they also faced pressure to respond to messages at all hours of the day—especially at secondary school when more youngsters have mobile phones.

    The Children's Commissioner said schools and parents must now do more to prepare children for the emotional minefield(雷区）they faced online. And she said social media companies must also "take more responsibility". They should either monitor their websites better so that children do not sign up too early, or they should adjust their websites to the needs of younger users.

    Javed Khan, of children's charity Bamardo's, said: "It's vital that new compulsory age-appropriate relationship and sex education lessons in England should help equip children to deal with the growing demands of social media.

    "It's also hugely important for parents to know which apps their children are using."

    If you want to become a fluent English speaker you should take some advice. There are four skills in learning English. They are reading, listening, speaking, and writing. The most important thing you must remember is that if you want to improve your speaking and writing skills, you should first master the skills of reading and listening.

    Read as much as you can. But your reading must be active. It means that you must think about the meaning of the sentence, the meaning of the unfamiliar(不熟悉) words, etc. There is no need for you to pay much attention to grammars or try to understand all the unfamiliar words you come across, but the fact that you see them for the first time and recognize them whenever you see them, for example, in other passages or books, is enough. It would be better to prepare yourself a notebook so you can write down the important words or sentences in it.

    As for listening, there are two choices: besides reading, you can listen every day for about 30 minutes. You can only pay attention to your reading and become skillful at your reading, then you can catch up on your listening. Since you have lots of inputs in your mind, you can easily guess what the speaker is going to say. This never means that you should not practice listening.

    For listening you can listen to cartoons or some movies that are specially made for children. Their languages are easy. Or if you are good at listening you can listen to VOA or BBC programs every day. Again the thing to remember is being active in listening and preferably taking some notes.

    If you follow these pieces of advice, your speaking and writing will improve quickly, and you can be a fluent English speaker one day.