No country in the world has more daily newspapers than the US. There are almost 2,000 of them, as compared with 180 in Japan, 164 in Argentina and 111 in Britain. The quality of some American papers is extremely high and their views are quoted all over the world. Famous dailies like the Washington Post or the New York Times have a powerful influence all over the country. However, they are not national newspapers in the sense that The Times is in Britain or Le Monde is in France, since each American city has its own daily newspaper. The best of these presents detailed description of national and international news, but many tend to limit themselves to state or city news.

    Like the press in most other countries, American newspapers range from the “sensational” which feature crime and gossip (闲谈), to the “serious”, which focus on factual news and the analysis of world events. But with few exceptions, American newspapers try to entertain as well as give information, for they have to compete with the attraction of television.

    Just as American newspapers satisfy all tastes, so do they also try to attract readers of all political parties. A few newspapers support extremist (极端主义的) groups on the far right and on the far left, but most daily newspapers try to attract middle-of-the-road Americans who are moderate (中立的). Many of these papers print columns by well-known journalists of different political and social views, in order to present a balanced picture.

    As in other countries, American newspapers can be either responsible or irresponsible, but it is generally accepted that the American press serves its country well and that it has more than once courageously exposed political scandals (丑闻) or crimes, for instance, the Watergate Affair (水门事件). The newspapers drew the attention of the public to the horrors of the Vietnam War.

    Many science fiction stories tell about explorers arriving in a new world. The explorers then use some kind of high-tech device to test for breathable air or signs of life. But here on Earth, science fiction is becoming reality through a new sampling technology called environmental DNA, or eDNA for short. Scientists can use it to identify rare species or estimate fish populations with just a little air or water.

    Environmental DNA can be used in two ways. One is to identify the creatures that live in a certain place. The other is to confirm the presence or lack of a specific creature.

    Caren Goldberg is one of the first biologists to take the technology from the testing stage to actually using it. She sees eDNA as a way to get answers more efficiently and with less destruction compared to traditional survey techniques. Until recently, scientists depended on snorkeling ( 潜水), netting or using an electric current to temporarily catch fish.

    This newer way to identify what lives in the environment is becoming popular around the world. Animal experts in Vietnam are using the eDNA to find the last, wild Yangtze giant softshell turtles. One researcher on the Caribbean island of Trinidad is using the sampling technology to find endangered golden treefrogs. In Madagascar, it is being used to identify amphibian(两栖动物)diseases.

    Ms Goldberg has used eDNA testing to confirm the local extinction (灭绝) of a leopard frog in the American state of Idaho. She has also been asked to document the spread of the New Zealand mudsnail in the state of Washington. The creature has been found in lakes and other waterways across the state.

    Scientists working with the technology say they do not expect robots to replace field biologists anytime soon. But the old-fashioned field work could soon be more targeted.

    We often ask these questions: Are African wild dogs really dogs? What's the difference between African wild dogs and the dogs we know as pets? For one thing, African wild dogs, which live in Africa, only have four toes, while domestic(驯养的）dogs and wolves have five. But you won't want to count for yourself, because they are truly wild animals.

    “Wild dogs are not somebody's domestic dogs that ran away and didn't come back, although some people used to think that,” explains Dr. MeNutt, who studies these animals at Wild Dog Research Camp in the African country of Botswana. “They are actually Africa's wolves, and just like wolves, and they do not make good pets. They need to be out in the wild doing what they are supposed to do — find the food they need to survive and feed their babies.” In fact, they travel so far that researchers have to use radio collars (颈圈) to keep track of them. The collars send out radio signals that tell people where the dogs are. No two wild dogs have the same pattern of coats, so it is easy to tell them apart.

    African wild dogs are smart and sociable, like pet dogs. Adult wild dogs, male and female, are willing to take good care of young ones.

    Millions of domestic dogs live on the planet, but there are probably fewer than 6000 African wild dogs left. Humans hunt them and farmers who don，t want them to go after cows and sheep poison them. Humans are also destroying the wild, natural habitat (栖息地) they need to survive in. Fortunately, today more farmers are finding other ways to protect their cows and sheep from African wild dogs instead of killing the animals.

    The earliest known copy of Leonardo da Vinci's Mona Lisa—thought to have been painted at the same time as the original masterpiece—has been discovered at the Prado Museum in Madrid, Spain. The work offers art-lovers an attractive clue to what the model for the world's most famous painting really looked like. Controllers of the museum found the picture hidden beneath layers of paints during restoration work on a picture initially thought to have been a later replica(exact copy) of the Mona Lisa.

    The restored version shows the same woman that Leonardo depicted (描画), against a landscape similar to that shown in the background of the original, which now hangs in the Louvre in Paris. And while the features of Leonardo's Mona Lisa have been dulled by centuries of dirt and layers of cracked paints—which are unlikely ever to be removed—in the recently-rediscovered copy, she appears fresher-faced and younger than her better-known "twin".

    News of the find was revealed at a meeting at London's National Gallery, linked to its "Leonardo da Vinci: Painter at the Court of Milan" exhibition. "This sensational (轰动的) find will transform our understanding of the world's most famous picture," the Art Newspaper reported, adding that the clues found on the Madrid version suggest that the original and the copy were begun at the same time and painted next to each other, as the work went on.

    Miguel Falomir, manager of Italian painting at the Prado, told reporters that expert analysis suggested a strong link between Leonardo and the artist who painted the copy. "The painting was done in the painter's own workshop," he said. "It is absolutely consistent with Leonardo's work, but Leonardo didn't actually do any work on it himself."

    A person can use all five senses while spending time with dolphins. We can see them play in the waves, hear them call, and feel their skin. Dolphins can sense you, too, but not in all the same ways. They have good eyesight, for example, but no sense of smell. Sensory biologists try to understand connections between animal behaviors and the senses. One team of these scientists recently made an unexpected discovery about certain dolphins.

    The researchers found that Guiana dolphins can detect electric fields, an ability that may help them find fish to eat. The secret to this newly found sense, say the scientists, is hidden in the dolphins' snouts (口鼻部).

    "We were really surprised to find this in the dolphin. Nobody had expected it," said Wolf Hanke, who led the new dolphin study.

    Hanke and his team suspected the dolphin's electro－sense might have something to do with small dimples (酒窝) on the animal's snout. "We thought they must have some functions," Hank said. To find out for certain, his team studied two Guiana dolphins.

    The scientists first studied the dimples of a 29－year－old dolphin that had died of natural causes. Under a microscope, the dimples looked familiar: they were similar to the sensors used by other animals to detect electric fields.

    Next, Hanke and his team tested a live dolphin, a 28－year－old named Paco, to see if he could recognize an electric field. They taught Paco to swim close to a device that could create a weak electric field in the water. Then the team taught Paco to swim away from the device if he detected any changes. When the scientists created an electric field, Paco swam away—showing that he knew something had changed. When there was no electric field, Paco stayed there. When Paco's snout was covered in plastic, he didn't react to the electric field.

    Paco's behavior told the scientists that the dolphin used his snout to detect the tiny electric field. "This is a major breakthrough," Peter Madsen, a sensory biologist, said.

    3D printing is becoming more and more popular. We are now able to print things such as clothing, musical instruments and so on.{#blank#}1{#/blank#} Some scientists are trying to revolutionize the dining experience by doing this. They hope that having a 3D printer in the kitchen will become as commonplace as the microwave or blender. Scientists say that they are easy to use: {#blank#}2{#/blank#} You can also modify the instructions to make the food exactly how you want it. This means that it would be very quick and easy to create tasty and nutritious meals.

    {#blank#}3{#/blank#}There would be less need for traditional growing, transporting and packaging processes as food production would be a lot more efficient.

    Printing food could also help people who suffer from dysphasia（言语困难）. They could program the printer to print softer versions of their favourite foods so that they would not have trouble swallowing them.

    However, some people think that a future of 3D-printed food would be a disaster. {#blank#}4{#/blank#}Imagine a world where there was no need for farming or growing crops and the same tastes and textures could be printed from a raw 'food ink'. Likewise, traditional cafes and restaurants might lose business.{#blank#}5{#/blank#} Is it really possible to get the nutrients we need from food-based inks and gels?

    What's more, cooking and eating together with family and friends will disappear. It is hard to imagine a world where the pastime of cooking is dead and meals can be created at the touch of a button.

A. It will create many jobs.

B. It could take away many jobs.

C. Also, there are concerns about the nutritional value of printed food.

D. You simply have to select a recipe and put the raw food 'inks' into the printer.

E. Using 3D printers to create your meals would also be saving the environment.

F. But can you imagine printing food?

G. Printing food is great for your health.