B

    Have you ever wondered why the roots of the plants always know which way to grow—into the soil but not above it? Some British scientists have recently solved this mystery.    

      It turns out that roots have special hairs that tie them into the soil and help them grow their way past obstacles, a team at the John Inners Center in Norwich reports in the February 29 issue of Journal Science.

    "The key is in the fuzzy(有绒毛的) coat of hairs on the roots of plants," says professor Liam Dolan. "We have found a growth control system that enables these hairs to find their way and to become longer when their path is clear."

    Root hairs explore the soil in much the same way a person would feel their way in the dark. If they come across an obstacle, they make their way around until they can continue growing in an opening. I the meantime, the plant is held in place as the hairs grip the soil.

    The hairs are guided by a clever chemical trick. A protein(蛋白质) at the tip of the root hairs called RHD2 helps them to take calcium(钙) from the soil. Calcium makes the hairs grow, and produce more RHD2, and take more calcium.

    But when an obstacle blocks the hair's path, or the hair reaches the surface of the soil, the cycle is broken and growth starts in another direction.

    This system gives plants the flexibility to explore a complex environment and to live in even the most unpromising soils, says Dolan.

    In poor soils such as in parts of Australia and Africa, native plants have adapted by producing enormous numbers of root hairs. A better understanding of this adaptation will allow scientists to develop hairy rooted crops that can grow in unfriendly environments.

    According to Dolan, "Research in the John Inners Center is taking a breeding approach(育种方法) to increase hair length in wheat but it will be some time before new cultivars(栽培变种) are developed."

    All languages change over time, but some change at a faster rate than others. {#blank#}1{#/blank#} The most important factors are the number of people who speak a language, where they live and whether they move around, the importance of the language for world trade and communication, and changes in technology.

    {#blank#}2{#/blank#} However, today English is the most widely used language in the world. English is spoken by about 350 million people as a first language in countries such as Great Britain, the United States. In addition, about a billion more people speak English as a second language.

    English started to take over French as an international language during the period of British colonialism (殖民主义) when the English ruled many countries in Africa and Asia. {#blank#}3{#/blank#} The colonial period came to an end at the same time that several other changes occurred. For example, the U.S. started to play a greater part in global affairs and the international economy. New means of communication technology such as television and the Internet spread English worldwide. {#blank#}4{#/blank#} In addition, they could use the Internet for information, business, or e-mail communication, all in English. Just as the use of English spread, other languages changed English by contact or by new inventions and technology.

    In contrast, Icelandic is a language that has changed very slowly. Icelandic speakers today can understand poetry written in a slightly different dialect over 1,000 years ago! Why has Icelandic changed so slowly? The main reason is the isolated (孤立的) location of the island in the middle of the Atlantic Ocean. {#blank#}5{#/blank#} Compared to England, Iceland had no history of colonialism. Iceland's small population has not played a major role in international trade or communication. Today, most Icelanders speak English in addition to their native language. With outside influences, Icelandic is changing more rapidly now.

A. People everywhere could watch the news or sports events in English.

B. These changes have a great influence on the development of society.

C. Isolation meant that for hundreds of years, Icelanders had little contact with speakers of other languages.

D. What are some of the factors that influence how quickly a language changes?

E. The language communication brings about the communication of technology.

F. In the past, other languages such as Latin or French were more important than English.

G. English was the primary means of communication in these colonies.

Londoners are great readers. They buy vast numbers of newspapers and magazines and of books — especially paperbacks, which are still comparatively cheap in spite of ever-increasing rises in the costs of printing. They still continue to buy "proper" books, too, printed on good paper and bound（装订）between hard covers.

    There are many streets in London containing shops which specialize in book-selling. Perhaps the best known of these is Charring Cross Road in the very heart of London. Here bookshops of all sorts and sizes are to be found, from the celebrated one which boasts of being "the biggest bookshop in the world" to the tiny, dusty little places which seem to have been left over from Dickens' time. Some of these shops stock, or will obtain, any kind of book, but many of them specialize in second-hand books, in art books, in foreign books, in books on philosophy, politics or any other of the countless subjects about which books may be written. One shop in this area specializes only in books about ballet!

    Although it may be the most convenient place for Londoners to buy books, Charring Cross Road is not the cheapest. For the really cheap second-hand books, the collector must venture off the beaten track, to Farringdon Road, for example, in the East Central district of London. Here there is nothing so impressive as bookshops. The booksellers come along each morning and pour out their sacks of books onto small hand carts. And the collectors, some professionals and some amateurs, have been waiting for them. In places like this they can still, occasionally, pick up for a few pence an old one that may be worth many pounds.

What is a boy?

    Between the innocence of babyhood and the seriousness of manhood we find a delightful creature called a "boy". Boys come in different sizes, weights, and colors, but all boys have the belief: to enjoy every second of every minute every hour of every day and to fill the air with noise until the adult males pack them off to bed at night.

    Boys are found everywhere—on top of, under, inside of, climbing on, swinging from, running around, or jumping to this and that! Mothers spoil them, little girls hate them, older sisters and brothers love them, and God protects them. A boy is TRUTH with dirt on its face. BEAUTY with a cut on its finger, WISDOM with chocolate in its hair, and HOPE of the future with a snake in its pocket.

    When you are busy, a boy is a trouble­maker and a noise. When you want him to make a good impression, his brain turns to jelly, or else he becomes a wild creature bent on destroying the world and himself with it.

    A boy is a mixture—he has the stomach of a horse, the digestion of stones and sand, the energy of an atomic bomb, the curiosity of a cat, the imagination of a superman, the shyness of a sweet girl, the brave nature of a bull, the violence of a firecracker, but when you ask him to make something, he has five thumbs (拇指) on each hand.

    He likes ice cream, knives, saws, Christmas, comic books, woods, water (in its natural habitat), large animals, Dad, trains, Saturday mornings, and fire engines. He is not much for Sunday schools, companies, schools, books without pictures, music lessons, neckties, barbers, girls, overcoats, adults, or bedtime.

    Nobody else is so early to rise, or so late to supper. Nobody else gets so much fun out of trees, dogs, and breezes. Nobody else can put into one pocket a rusty knife, a half eaten apple, a three­foot rope, six cents and some unknown things.

    A boy is a magical creature—he is your headache but when you come home at night with only shattered pieces of your hopes and dreams, he can mend them like new with two magic words, "Hi, Dad!"

On an autumn afternoon, a remote sheep farm in southern Greenland is quiet. The silence is abruptly broken when dozens of sheep come thundering across the hills overlooking the farm. Walking after them are Lars Nielsen and his 37-year-old son Kunuk Nielsen.

The Nielsen family has owned and run the farm since 1972. Kunuk says the summers now are longer than when he was a child and that drought has become a problem. The fields are not so green as those in the old days. He has to buy hay (草料) from European countries.

The effects of a warming climate are obvious on the land. While he intends to struggle on, his older brother Pilu has chosen a different path.

Pilu, 40, lives in Qaqortoq in the south of Greenland -- a town of about 3,000 people. Ten years ago, he got his helicopter pilot's license and is now part owner of a small company called Sermeq Helicopters. It caters to construction and telecommunication workers and an increasing number of foreign tourists.

Pilu says he loves his family's sheep farm. But he saw that warming temperatures were making remote areas of Greenland more accessible and wanted to look for other opportunities. His company's most popular tours include a visit to Greenland's glaciers.

The warming temperatures are also affecting traditional ways of life, particularly hunting. The sea ice is changing; it's becoming less so that hunting on ice becomes more difficult. When there's no sea ice, it's difficult to use dog sledges (雪橇), and the whole culture around having dogs and dog sledges and doing traditional hunting on the ice is sort of diminishing.

Besides, many Greenlanders, like Pilu, are leaving the countryside for towns and the capital city Nuuk, where opportunities are greater. A report found that Nuuk's share of Greenland's population grew from 17.2% in 1977 to 29.2% in 2014. If there were enough houses in Nuuk, the share would even be bigger.

The Mona Lisa is one of the most famous paintings in the world. Painted by Leonardo da Vinci in the early 16th century, it has captivated audiences for centuries with its mysterious smile and masterful technique. 

The painting is housed in the Louvre Museum in Paris, France, and attracts millions of visitors each year. However, the Mona Lisa's history is not without controversy. There have been numerous attempts to steal or deface the painting, and its conservation has been a subject of great concern.

Leonardo da Vinci's use of sfumato, a technique that blends colors and tones seamlessly, gives the painting a soft and hazy appearance. The sitter's expression, which seems to change depending on the viewer's angle and mood, adds to the intrigue of the work.