It is bad to have food stuck between your teeth for long periods of time. This is because food attracts germs; germs produce acid, and acid hurts your teeth and gums. Flossing (使用牙线) helps to remove the food that gets stuck between your teeth. This explains why flossing helps to keep your mouth healthy, but some doctors say that flossing can also be good for your heart.

    It may seem strange that something you do for your teeth can have any effect on your heart. Doctors have come up with a few ideas about how flossing works to keep your heart healthy. One idea is that the germs that hurt your teeth can leave the mouth and travel into your blood.Germs that get into the blood can then attack your heart. Another idea is based on the fact that when there are too many germs in your mouth, the body tries to fight against there germs. For some reason, the way the body fights these mouth germs may end up weakening the heart overtime.

    Not every doctor agrees about these ideas. Some doctors think that the link between good flossing habits and good heart health is only a coincidence. The incidence (发生率) of two or more events is completely random, as they do not admit of any reliable cause and effect relationship between them. For example, every time I wash my car, it rains. This does not mean that when I wash my car, I somehow change the weather. This is only a coincidence. Similarly, some doctors think that people who have bad flossing habits just happen to also have heart problems, and people who have good flossing habits just happen to have healthy hearts.

    The theory that flossing your teeth helps to keep your heart healthy might not be true. But every doctor agrees that flossing is a great way to keep your teeth healthy. So even if flossing does not help your heart, it is true to help your teeth. This is enough of a reason for everyone to floss their teeth every day.

    “People are ruder today because they are rushed and more 'time poor' than ever before，” says Patsy Rowe, “Manners_have_fallen_off_the_radar(雷达)．” Due to our strong attraction to electronic equipment it is a wonder more people don't wake up each morning and greet the singing birds with a complaint(抱怨)about the noise. Here are some examples of rudeness.

    Some people prefer to do almost everything over the Internet. To them, dealing with an actual human needs more patience. It feels very slow because humans don't work at 4G speeds. When you have dinner with friends, you will often notice someone paying more attention to his mobile phone. We have programmed ourselves to think that every new message brings life－changing news, so taking calls and checking our texts are more important than talking to the people we are with. What is worse, some people even tend to send anonymous(匿名的) rude messages by email.

    However, rudeness is never acceptable. Don't assume it is OK to be rude if the person you're in touch with won't recognize you. If you have something awful to say, have the courage to face the person and say it, write a letter or email and sign it, or forget it. Upsetting people with unsigned messages is cruel and disgusting.（令人厌恶的）

    We shouldn't blame technology for our shortcomings. Technology is here to help us，but we should not allow it to take over our lives. An important step is acknowledging our shortcomings. People spend a lot of time pointing out bad manners but it would be even more helpful if we'd publicly acknowledge good manners when we see them.

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    Welcome to your future life!

    You get up in the morning and look into the mirror. Your face is firm and young-looking. In 2035, medical technology is better than ever. Many people of your age could live to be 150, so at 40, you're not old at all. And your parents just had an anti-aging (抗衰老的) treatment. Now, all three of you look the same age!

    You say to your shirt, “Turn red.” It changes from blue to red. In 2035, “smart clothes” contain particles(粒子) much smaller than the cells in your body. The particles can be programmed to change clothes' color or pattern.

    You walk into the kitchen. You pick up the milk, but a voice says, “You shouldn't drink that!” Your fridge has read the chip (芯片) that contains information about the milk, and it knows the milk is old. In 2035, every article of food in the grocery store has such a chip.

    It's time to go to work. In 2035, cars drive themselves. Just tell your “smart car” where to go. On the way. You can call a friend using your jacket sleeve. Such “smart technology” is all around you.

    So will all these things come true? “For new technology to succeed,” says scientist Andrew Zolli, “it has to be so much better that it replaces what we have already.” The Internet is one example. What will be the next?

    To save as much language diversity as possible in the face of its rapidly dying out, researchers suggest using “evolutionary trees”, a tool from conservation biology.

    One of the world's 7,000 languages disappears every other week, and half might not survive the 21st century, experts say.

    When setting conservation goals, ecologists use evolutionary trees—diagrams that show how biological species are related to one another—to identify species that have few close relatives. Such species are said to be evolutionarily distinct. Similarly, recent advances in the construction of language trees make it possible to measure how unique a language is.

    “Evolutionary trees have transformed our understanding of how life has evolved and helped us to decide which species most need conserving,” says Jonathan Davies, senior author of the new study.

    “The rapid rate of language loss, as well as limited resources for preservation（保护）, means that we must choose carefully where to focus our efforts,” adds Max Farrell, a PhD student in Davies' lab. “The more isolated (孤立的) a language in its family tree, the more unique information it contains and eventually contributes to language diversity.”

    As a case study, they used this approach to rank 350 Austronesian languages, spoken in islands spread across Southeast Asia and the Pacific Ocean.

    For each of these languages, the researchers combined measures of evolutionary distinctiveness (ED) and global endangerment (GE) to produce an “EDGE” score. The language with the highest score, which means it is extremely distinct（不同的） yet nearly dying out, was Kavalan, a language native to Tai Wan. The next-highest scores went to Tanibili, an endangered language in the Solomon Islands.

    By building trees for other language groups, language specialists could target preservation efforts and help reduce the loss of language diversity in the future, the researchers say.

    Benjamin West, the father of American painting, showed his talent for art when he was only six years of age. But he did not know about brushes before a visitor told him he needed one. In those days, a brush was made from camel's hair. There were no camels nearby. Benjamin decided that cat hair would work instead. He cut some fur from the family cat to make a brush.

    The brush did not last long. Soon Benjamin needed more fur. Before long, the cat began to look ragged（蓬乱）. His father said that the cat must be sick. Benjamin was forced to admit what he had been doing.

    The cat's lot was about to improve. That year, one of Benjamin's cousins, Mr. Pennington, came to visit. He was impressed with Benjamin's drawings. When he went home, he sent Benjamin a box of paint and some brushes. He also sent six engravings（版画） by an artist. These were the first pictures and first real paint and brushes Benjamin had ever seen. In 1747, when Benjamin was nine years old, Mr. Pennington returned for another visit. He was amazed at what Benjamin had done with his gift. He asked Benjamin's parents if he might take the boy to Philadelphia for a visit.

    In the city, Mr. Pennington gave Benjamin materials for creating oil paintings. The boy began a landscape(风景) painting. William Williams, a well-known painter, came to see him work. Williams was impressed with Benjamin and gave him two classic books on painting to take home. The books were long and dull. Benjamin could read only a little, having been a poor student. But he later said,＂ Those two books were my companions by day, and under my pillow at night.＂ While it is likely that he understood very little of the books, they were his introduction to classical paintings. The nine-year-old boy decided then that he would be an artist.

    Little black taxis, often run-down and falling apart from decades of use, have for a long time been a main feature of Cairo's chaotic urban landscape. But their days may be numbered, thanks to a new taxi replacement programme aimed at knocking out older, potentially unsafe vehicles.

    The government-sponsored action, launched earlier this year, allows drivers of taxis 20 years or older, mostly Fiats and Peugeots, to trade their cars for shiny new all-white ones at generous rates of financing. Drivers can choose between five different locally manufactured car models.

    According to officials, more than 11,000 brand new taxis, sporting trademark checked stripes on the sides, have already hit the streets of the capital, and they've been welcomed enthusiastically by passengers. Many people say that not only are the new taxis more comfortable, but they also make the streets of Cairo far more presentable. Furthermore, taxi fares have only increased by a small amount.

    The poor condition of most black and white taxis is almost legendary. Passengers often have to deal with windows and doors that do not open and close, and heavy, thick petrol gases. Air conditioning is unheard of. The new all-white taxis, meanwhile, are cleaner, more fuel-efficient and provide air conditioning on request. Furthermore, all the new taxis come equipped with functioning fare meters, which avoids arguments and sometimes fights with passengers!

    The government hopes to replace all of the capital's 40,000 elderly black cabs soon, but not everyone in Cairo will be happy to see them go. Hotel manager Ibrahim Al-Toukhy says that the old black cabs were weak and run-down, and maybe even a little dangerous, but they were part of the city, and part of Cairo's character.