If you need help herding some sheep or retrieving a stick, you can count on your canine companion(伴犬) because dogs always seem to be keen on lending a paw. But only if their partner is a person. When it comes to cooperating with one another, dogs are truly lost－and instead it’s wolves who’ve mastered the art of teamwork. That’s according to a study in the Proceedings of the National Academy of Sciences.

For thousands of years, humans have been breeding (饲养) dogs that can do all sorts of neat tricks. And because dogs aim to please, we’ve come to think that domestication(驯养) has somehow boosted dogs’ powers of cooperation. But researchers in Austria have been wondering whether that idea could be barking up the wrong tree. Because left to their own devices, dogs are bigger loners than wolves.

“So wolves live in closely knit family packs, they cooperate in raising the young, they also cooperate in hunting and in defending their territories. So they really have a strong dependence on cooperation in many aspects of their lives. In contrast, to this free ranging dogs actually forage (觅食) mostly by themselves. It’s only mothers that raise their young. And they do form packs but they tend to be somewhat more fluid(不固定的), if you want.”

That’s Sarah Marshall-Pescini of the Wolf Science Center at the University of Vienna. She and her colleagues decided to test dogs’ and wolves’ relative powers of cooperation. In the setup, a pair of animals—either two dogs or two wolves—is presented with a contraption(装置) that will allow the participants to access a plate of food—but only if both members of the team pull on the two ends of a rope at the same time.

A dozen wolves and 14 dogs took the challenge. And the results? The wolves ran circles around their doggie descendants. In some 400 attempts, the wolf teams scored a snack 100 times. Which may not sound all that impressive…until you compare it with the doggie duos, who, in nearly 500 trials, succeeded only twice.

Now, it’s not that dogs are less avid learners. Or that they turned tail and avoided the apparatus. Marshall-Pescini says the dogs were curious about the device.

“What seemed to be happening was they didn’t want to get into conflict with each other. So they wouldn’t both go and try things on it but rather took it in turns. And this really hindered(阻碍了) their capacity to cooperate.”So rather than step on each others’ toes, the dogs took turns bowing out, giving their teammate a chance at the plate. That show of social grace left the poor dogs with their tummies growling (饥肠辘辘). And no treat to wolf down.

(Source:Scientific American Oct. 25, 2017)

Special trees that grow faster, fight pollution, produce better wood, and even sense chemical attacks are being planted by scientists in the US.

When 40 percent of Hawaii's US$14 million-a-year papaya (木瓜)industry was destroyed by a virus（病毒）five years ago, work began on creating genetically engineered(转基因的) trees.

Researchers successfully introduced seeds that were designed to resist the virus. Since then, more and more people have been testing genetically engineered trees.Some researchers put special bacteria into trees to help them grow faster and produce better wood. Others are trying to create trees that can clean polluted soil.Meanwhile fruit farmers are looking for trees that are strong enough to resist worms, and paper companies want trees that produce more wood and therefore more paper.

The Pentagon (五角大楼) even gave the researchers US$500,000 this year after they developed a pine tree that changes its colours if it senses a chemical attack..So far,the poplar, eucalyptus (杨树与桉树), apple and coffee trees are among those being engineered. All this can be done today because we have a better understanding of tree genomes(基因组).

However, some people fear that the genetically engineered trees will cause dangerous results. They are worried that the new trees will breed() with natural species and change the balance of the forest environment.

"It could be destructive," said Jim Diamond, an environmentalist. "Trees are what is left of our natural environment and home to many endangered species."

But researchers insist that science could give nature a fighting chance against both natural and man-made dangers.They hope to answer the critics by stopping the new trees from breeding, so their effect on the environment can be controlled.

This is Copycat, a kitten who will go down in history. The two-month-old kitten, with blue eyes and a pink button nose, looks like any other kitten. But Copycat is a pioneer of commercial (商业的，盈利的)cloning. She means that cats of the future could have more than nine lives.

The company which produced her ---by the same technique as Dolly the Sheep ---plans to charge wealthy pet owners thousands of pounds to replicate （复制）animals that have died. They are already working on a cloned dog.

Copycat was created in a laboratory at the Texas A&M University. She is a copy of an adult cat from which DNA was removed, and is quite different from the surrogate mother（代孕母亲）who gave birth to her. Despite having identical genes to the adult cat, Copycat has slightly different patterns on her cream and coat（皮毛）. The Texas team say this is because the patterns are the result of the kitten’s natural development as well as genetics（遗传）.

Copycat’s creation was financed by 81-year-old John Sperling, who owns a company called Genetic Savings & Clone. He plans to offer the technology to wealthy people seeking to replace beloved pets. He also wants to replicate “socially-valuable” animals such as search-and-rescue dogs.

Experts predict that commercial pet cloning will become widely available in just a few years and claim that it will be the first breakthrough in the field to directly benefit the public. However, the breakthrough raises more concerns about how cloning techniques are being used. Critics have considered the work as disturbing the mature and a waste of scientific resources. They warn that cloned pets, even if they are genetically identical to the animals they are meant to replace, could be quite different in character and behavior. The UK’s Animal Procedures Committee says cloning for “trivial purposes” such as pets should be banned and that cloning should be used to help people solve some big and life-threatening problems.

Electric cars are dirty. In fact, not only are they dirty, they might even be more dirty than their gasoline-powered cousins. 

People in California love to talk about “zero-emissions (排放) vehicles”, but people in California seem to be clueless about where electricity comes from. Power plants mostly use fire to make it. Aside from the new folks who have their roofs covered with solar cells, we get our electricity from generators (发电机). Generators are fueled by something--usually coal, oil, but also by heat generated in nuclear power plants. There are a few wind farms and geothermal (地热)plants as well, but by far we get electricity mainly by burning something.

In other words, those "zero-emissions" cars are likely coal-burning cars. It’s just because the coal is burned somewhere else, it looks clean. It is not. Itˈs as if the California Greens are covering their eyes—“If I canˈt see it, itˈs not happening.” Gasoline is an incredibly efficient way to power a vehicle; a gallon of gas has a lot of energy in it. But when you take that gas（or another fuel）and first use it to make electricity, you waste a nice part of that energy, mostly in the form of wasted heat—at the generator, through the transmission lines, etc.

A gallon of gas may propel your car 25 miles. But the electricity you get from that gallon of gas wonˈt get you nearly as far— so electric cars burn more fuel than gasoline-powered ones. If our electricity came mostly from nukes or geothermal, or hydro or wind or solar, then an electric car truly would be clean. But for political, technical, and economic reasons, we donˈt use much of those energy sources. 

In addition, electric carsˈ batteries which are poisonous for a long time will eventually end up in a landfill. And finally, when cars are the polluters, the pollution is spread across all the roads. When itˈs a power plant, though，all the junk is in one place. Nature is very good at cleaning up when things are too concentrated, but it takes a lot longer when all the garbage is in one spot. 

China is embracing an era of sharing economy. After sharing bikes, sharing books are the next trend. The book-sharing program at Sanxiaokou Xinhua Bookstore in Hefei, capital of Anhui province, has been running for several months since its launch on July 16, 2017. Customers are encouraged to borrow up to two books, from all books available in this store, for free via an app, pay 99 yuan online as the deposit and return the books within 10 days.

A survey of 601 app users conducted by the company in late July found that more than 90 percent of the readers said they may want to keep some of the borrowed books permanently, but they donˈt want to visit the store again to complete the purchase. When another nine stores joined the book-sharing program in August, the ability to purchase the borrowed books was made available on the app.

Zhao Shiping, a manager of the Sanxiaokou store, said that the daily customer flow in the first week of the book-sharing program was about 7,000 while the figure for the same period last year was 5,000 to 6,000. So, book-sharing will reduce barriers for book purchasing and increase customer flow, which will increase the business value of the bookstore, its brand value and increase its value as a partner for companies outside the book sales sector.

In addition to bookstores, banks have also joined the trend of book-sharing. Two branches of China Everbright Bank introduced book loan service at the end of this July. The service is free for seven days and 0.1 yuan is charged after that and 0.5 yuan after 21 days. Readers can return borrowed books to any branch of the bank.

This book-sharing project, a cooperation between Everbright Bank and an app called Youshugongdu, which translates as "letˈs read books together", will be expanded to other outlets to turn each outlet into a small community library with 1,000 to 2,000 books.

①Increasing the customer flow

②Bringing convenience to the bookstores

③Reducing the barriers for book purchasing

④Increasing the brand value of the bookstores

B

Fear may be felt in the heart as well as in the head，according to a study that has found a link between the cycles of a beating heart and the chance of someone feeling fear.
　　Tests on healthy volunteers found that they were more likely to feel a sense of fear at the moment when their hearts are contracting(收缩)and pumping blood around their bodies，compared with the point when the heartbeat is relaxed. Scientists say the results suggest that the heart is able to influence how the brain responds to a fearful event，depending on which point it is at in its regular cycle of contraction and relaxation.
　　Sarah Garfinkel at the Brighton and Sussex Medical School said：“Our study shows for the first time that the way in which we deal with fear is different depending on when we see fearful pictures in relation to our heart.”
　　The study tested 20 healthy volunteers on their reactions to fear as they were shown pictures of fearful faces. Dr Garfinkel said，“The study showed that fearful faces are better noticed when the heart is pumping than when it is relaxed. Thus our hearts can also affect what we see and what we donˈt see—and guide whether we see fear.”
　　To further understand this relationship，the scientists also used a brain scanner to show how the brain influences the way the heart changes a personˈs feeling of fear.
　　“We have found an important mechanism by which the heart and brain ‘speak’ to each other to change our feelings and reduce fear，” Dr Garfinkel said.
　　“We hope that by increasing our understanding about how fear is dealt with and ways that it could be reduced, we may be able to develop more successful treatments for anxiety disorders，and also for those who may be suffering from serious stress disorder.”

Paragraph 6?　

C

I am Peter Hodes, a volunteer stem cell courier. Since March 2012, I've done 89 trips — of those, 51 have been abroad. I have 42 hours to carry stem cells (干细胞) in my little box because I've got two ice packs and that's how long they last. In all, from the time the stem cells are harvested from a donor (捐献者) to the time they can be implanted in the patient, we've got 72 hours at most. So I am always conscious of time.

I had one trip last year where I was caught by a hurricane in America. I picked up the stem cells in Providence, Rhode Island, and was meant to fly to Washington then back to London. But when I arrived at the check-in desk at Providence, the lady on the desk said: "Well, I'm really sorry, I've got some bad news for you—there are no flights from Washington." So I took my box and put it on the desk and I said: "In this box are some stem cells that are urgently needed for a patient—please, please, you've got to get me back to the United Kingdom." She just dropped everything. She arranged for a flight on a small plane to be held for me, re-routed (改道) me through Newark and got me back to the UK even earlier than originally scheduled.

For this courier job, you're consciously aware that in that box you've got something that is potentially going to save somebody's life.

Which of the following can replace the underlined word "courier" in Paragraph 1?