When early humans killed a mammoth, how did they keep the meat before they could eat it all? We don’t know; maybe they didn’t. But perhaps they preserved their mammoth steaks in salt. However, it is hard to know for sure. We do know for certain that by 3,000 years ago, the Babylonians, Egyptians, and Chinese were all experts at salting. They used salt to preserve food.
For thousands of years, salting was a common way to preserve food. But for a long time, no one knew why salt worked. Then, in the 1800s, a Frenchman named Louis Pasteur discovered the secret: bacteria. What does salt have to do with bacteria? First, bacteria need moisture to grow and multiply. Salt pulls moisture out of food, so the bacteria no longer have enough moisture. Besides, salt is poisonous to many bacteria. If you cover food with salt, bacteria outside the food die before they get in, and bacteria already in the food are poisoned by the salt.
So how do you preserve food with salt? For meat or fish, you pour on a layer of salt, then rub it in well. Hams are often made this way. Another way is to alternate layers of food and salt in a big container. The salt will draw the moisture out of the food, creating a brine that the food sits in. You’ll need to make sure the brine completely covers the food; any food left exposed to the air will spoil. If you preserve cabbage this way, you’ll make sauerkraut.
How well salt preserves food depends on how much is used. The more salt, the longer the food is preserved. Unfortunately, using enough salt to preserve food for a very long time can cause problems. It can make food tough. It can destroy flavor. And, of course, it can make the food too salty to eat, which is harmful to our health.
Today, even though we no longer rely on salt to keep our food fresh, we haven’t lost our taste for salt. We don’t want to give up our bacon, salami, and watermelon pickles!
1. Why are examples of the ancient people mentioned in the first paragraph?| A．To make an introduction to the topic. |
| B．To explain our ancestors were very clever. |
| C．To tell us the ancient people had a lot of food to eat. |
| D．To show the ancient people were good at preserving food. |
| A．If you want to make a ham, you should keep it in a brine. |
| B．If you want to make sauerkraut, you’d better pour on a layer of salt and rub it. |
| C．To keep our food longer, you should put as much salt on the food as possible. |
| D．People needn’t give up salty food completely as long as they control the amount. |
| A．To explain how the ancient people preserve food. |
| B．To tell us how salt works in preserving food. |
| C．To persuade people to give up salty food. |
| D．To introduce the way of preserving food with salt. |
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【推荐1】Sleep apnea is when you have pauses in breathing while you’re asleep. These pauses can last from seconds to minutes. You may have difficulty breathing a few times or dozens of times an hour. These breathing pauses can be dangerous if they cause the oxygen level in your body to drop or disturb your sleep. When oxygen drops, your brain does whatever it can to get you to resume breathing. And then you may snore (打鼾) , gasp, or make a choking sound.
Sleep apnea is a common disorder. Anyone can develop it. “Sleep apnea can occur in both sexes, in all races, and in people of all sizes and shapes,” says Dr. Michael Twery, a sleep expert.
So, how can you tell whether you may have this disorder? One of the most common symptoms is excessive (过多的) daytime sleepiness. “Anyone who feels so tired on a regular basis — even if they allow enough time to get enough sleep on a regular basis and they still feel this way — needs to discuss it with their doctor,” says Twery.
Another common symptom is loud, frequent snoring. But not everyone who snores has sleep apnea. Other symptoms of sleep apnea may include feeling impatient or depressed, or having mood swings. You may have memory problems or trouble concentrating. Or, you may wake up with a headache or a dry mouth.
Your doctor can diagnose sleep apnea based on your symptoms. A sleep study, which records things like heart rate and oxygen level while you sleep, can show whether apnea is mild or severe. “The largest amount of the population with sleep apnea has mild sleep apnea,” Twery explains. “Mild sleep apnea may or may not be associated with any daytime symptoms. People who are so sleepy that they’re at risk of a driving accident are probably in the moderate (中等的) to severe range.”
1. What does the underlined word “resume” in Paragraph 1 mean?| A．Avoid. | B．Continue. | C．Adjust. | D．Control. |
| A．find it difficult to breathe while walking | B．have a lower oxygen level in their body |
| C．feel tired and sleepy during the day | D．have a stable mood during the day |
| A．By making comparisons. | B．By listing some examples. |
| C．By analyzing some facts. | D．By following the order of importance. |
| A．It may cause heart problems. | B．It affects the majority of people. |
| C．It is highly dangerous for drivers. | D．It rarely shows any daytime symptoms. |
While some jobs may require talent, the ability to work as a team is learned. There are no complicated formulas(规则); you don't need to have any special qualities or exceptional mental abilities. Individuals can be effective as a team if they have developed certain behaviors or habits of communication. Many companies, clubs and organizations use team building activities. Team building activities may include a number of teamwork elements. They are aimed at encouraging active participation in task accomplishment while all members have their roles as individuals and are able to co-operate towards a common goal as a team.
Many team building activities focus on problem solving and discussing team issues; thus argument as a way to common consensus (共识) is encouraged. Team building activities often involve recognition and identification of team member skills, talents, knowledge, and experiences which allow the team members to learn more about each other and fully utilize (利用) those skills where appropriate（合适的）. Many team activities are focused on developing keys to trust during challenging times.
1. In the author's opinion, which of the following is important for a company to be successful?
| A．Specialized knowledge. | B．Highly-skilled staff. |
| C．Exceptional talent. | D．Teamwork skills. |
| A．require special qualities and abilities |
| B．are learned while working in a team |
| C．need exceptional mental abilities |
| D．are quite complicated to learn |
| A．hiring employees with special talent |
| B．encouraging employees to co-operate |
| C．helping employees work independently |
| D．training employees in their special fields |
| A．Team Building | B．Problem Solving |
| C．Communication Skills | D．Company Management |
【推荐3】“You’re so smart!” This encouraging response to children’s math performance is commonly heard. Recently, a new study, conducted by the University of Georgia, found that encouraging children with responses related to their personal characteristics or inborn abilities might weaken their math motivation and achievement over time.
Parents who make comments linking their children’s performance to personal characteristics like intelligence are using what’s referred to as person responses. In contrast, parents who link their children’s actions, such as efforts or strategy use, to their performance are using process responses.
For the study, researchers asked more than 500 parents to report on how they responded to their children’s math performance and their math beliefs and goals. Children were assessed in two waves across a year to measure their math motivation and achievement.
The results show that parents who view math ability as changeable are more likely to give process responses focused on their children’s strategy use and efforts rather than their intelligence or other personal characteristics. In contrast, parents who believe math ability is unchangeable and that math failure can’t be constructive give more person responses. Parents with high expectations for their children give a combination of both responses. While responses highlighting strategy and efforts are not related to any achievement outcomes, children who receive more responses about their personal characteristics -- in particular, related to failure -- are more likely to avoid harder math problems, exhibit higher levels of math anxiety, and score lower on math achievement tests.
Because person responses predict poor math adjustment in children over time, researchers suggest parents limit this type of responses at home. Another recommendation for parents is to think about their own beliefs and goals for their kids and examine how these might lead them to respond in person or process ways. Simply telling parents to avoid talking about math ability may not be enough. Focusing less on how children perform and more on their strategy and enjoyment of math might be a more effective way to enhance motivation.
1. Which of the following is an example of process response?| A．You are a lucky dog. | B．Running is in your blood. |
| C．What works well for your study? | D．Why are you such a math genius? |
| A．Parents prefer to give more process responses. |
| B．Children are more likely to be affected by math anxiety. |
| C．Process responses help with children’s math achievement. |
| D．Person responses can discourage children from learning math. |
| A．Restrict person responses. | B．Defend their own beliefs. |
| C．Stress children’s performance. | D．Ignore children’s math problems. |
| A．The Strategy Children Adopt to Learn Math Helps |
| B．The Way Parents Talk to Children on Math Matters |
| C．Responses to Enhance Children’s Math Performance |
| D．Suggestions for Parents to Teach Their Children Math |
【推荐1】Killer whales(虎鲸), also known as orcas, are known for their severe attacks(攻击) on sea animals but they have never posed a threat to humans. However, since late July, the normally social animals have been intentionally attacking sailboats off the coasts of Spain and Portugal.
The strange behavior first surfaced on July 29, 2020, when a 46foot boat was repeatedly attacked for almost an hour by nine orcas, causing the boat to rotate (旋转) 180 degrees and having its engine switched off. Since then, over 30 more similar incidents have been reported. On September 23, 2020, Spain’s government banned boats of less than 50 feet in length from sailing in the 60mile stretch of the Atlantic coastline between Ferrol and the Estaca de Bares Cape, where the attacks have been occurring.
Researchers across the world are trying to explain the orcas’ behavior. Some believe it could be a result of the overfishing of the bluefin tuna—the orcas’ primary food source—which has left the area’s killer whales starving and unable to feed their babies. “I saw them look at boats carrying fish. I think they know humans are somehow related to food shortages,” says Ken Balcomb, senior scientist at the Center for Whale Research in Washington, USA. The environmentalists believe the sudden increase in boat traffic after months of absence due to restrictions on human activity last spring, could also be contributing to the agitation.
However, Alfredo López, a biology professor in Galicia, Spain, thinks the attacks are defensive measures the orcas took to protect themselves against boat injuries. The researcher came to this conclusion after looking at the videos of a few incidents and noticing that two of the young killer whales involved had serious injuries. Hopefully, the experts will be able to find a way to restore the harmony between the animals and the humans soon.
1. What do we know about orcas in paragraph 1?| A．They are friendly to humans. |
| B．They have changed their behavior. |
| C．They are famous for hunting skills. |
| D．They have met tough living conditions. |
| A．Ken Balcomb. | B．The environmentalists. |
| C．Alfredo López. | D．Spain’s government. |
| A．The attacks. | B．Food shortages. |
| C．The overfishing. | D．Human activity. |
| A．A disagreement between scientists. |
| B．Possible reasons why killer whales are attacking boats. |
| C．The results of the change of the behaviors of killer whales. |
| D．Spanish government’s effort of protecting the fishing boats. |
【推荐2】Living and dealing with kids can be a tough job these days, but living and dealing with parents can be even tougher.
If I have learned anything in my 16 years, it is that communication is very important, both when you disagree and when you get along. With any relationship, you need to let other person know how you are feeling. If you are not able to communicate, you drift apart()疏远). When you are mad at your parents, or anyone else, not talking to them doesn’t solve anything.
Communication begins with the concerns of another. It means that you can’t just come home from school, go up to your room and ignore everyone. Even if you just say “Hi”, and see how their day was for five minutes, it is better than nothing.
If you looked up the word “communication” in a dictionary, it would say “the exchange of ideas, the conveyance（表达）of information, correspondence （通信）, means of communication: a letter or a message”. To maintain (保持) a good relationship, you must keep communication strong. Let people know how you feel, even if it’s just by writing a note.
When dealing with parents, you always have to make them feel good about how they are doing as a parent. If you are trying to make them see something as you see it, tell them that you’ll listen to what they have to say, but ask them politely to listen to you. Yelling or walking away only makes the situation worse.
This is an example: one night, Sophie went to a street party with her friends. She knew she had to be home by midnight after the fireworks, but she didn’t feel she could just ask to go home. That would be rude. After all, they had been nice enough to take her along with them. Needless to say, she was late getting home. Her parents were mad at first, but when Sophie explained why she was late, they weren’t as mad and let the incident go. Communication is the key factor here. If Sophie’s parents had not been willing to listen, Sophie would have been in a lot of trouble.
Communication isn’t a one-way deal: it goes both ways. Just remember: if you get into a situation like Sophie’s, telling the other person how you feel and listening is the key factor to communication.
1. In the writer’s view, dealing with parents is __________ than with children.| A．more difficult | B．easier |
| C．more uninteresting | D．more interesting |
| A．the importance of friendship | B．to make your feeling known to others |
| C．the importance of communication | D．the disagreement between generations |
| A．Sophie’s parents are willing to listen to her |
| B．Sophie is very polite to her parents |
| C．Sophie did well in explaining her being late |
| D．communication is the solution(解决办法) to misunderstanding |
| A．If you don’t agree with others, you’d better let them know |
| B．It is better to say “Hi” to others than say nothing |
| C．If you are not able to communicate, walk away |
| D．Communication is a two-way deal |
【推荐3】Strangers Under the Same Roof
Does every dinner with your parents seem to turn into an argument? Have your once warm and open conversations become cold and guarded? Do you feel that you just cannot see eye to eye with them on anything? You are not alone. Heated arguments and cold silences are common between teenagers and their parents.
Teenagers’ physical changes may result in such family tensions. You may feel anxious that you are not developing at the same rate as your friends, shooting up in height or getting left far behind. You might worry about your changing voice, weight problems or spots(粉刺). When the worries get too much, your parents are often the first target of your anger.
It can be a big headache to balance your developing mental needs too. You enter a strange middle ground—no longer a small child but not quite an adult. You have both a new desire for independence and a continued need for your parents’ love and support. You feel ready to be more responsible and make decisions on your own. Unfortunately, your parents do not always agree and that makes you feel unhappy. Sometimes they forget that growing up is a rough ride. It can be difficult when your parents treat you like a child but expect you to act like an adult. All of this can lead to a breakdown in your relationship.
Despite the fact that sometimes it may seem impossible to get along as a family, you can take action to improve the situation. The key to keeping the peace is regular and honest communication. Just remember that it is completely normal to struggle with the stress that parent-child tensions create, and that you and your parents can work together to improve your relationship. The good news is that this stormy period will not last. Everything will turn out all right in the end, and the changes and challenges of your teenage years will prepare you for adulthood.
1. Why does the author mention the questions in Paragraph 1?| A．To express his doubts. |
| B．To compare different ideas. |
| C．To introduce points for discussion. |
| D．To draw readers’ attention to the topic. |
| A．Between a child and an adult. |
| B．A small child. |
| C．An adult. |
| D．An old man. |
| A．Parents should let go of the control over their teenagers. |
| B．Teenagers should always follow their parents’ points of view. |
| C．Parents and teenagers should always keep open conversations. |
| D．Teenagers should not depend on their parents’ love or support. |
| A．Indifferent. | B．Critical. |
| C．Positive. | D．Negative. |
【推荐1】One day,I was taking a nap in my office when I woke up to the sound of a car crash.I sat up and looked out of the window.In the parking lot,a car had just crashed into a fence.The car must have been moving fast,because it was in bad shape.
Then I watched as the driver got out of the car.He wore loose trousers and a crumpled(褶皱的）shirt unbuttoned to show his chest hair.Immediately,I disliked him.
Then,he opened the passenger door,from which a very small child ran out.A kid in the front seat!My dislike for the man increased greatly.
As the child ran around in the parking lot,the man tried to repair the damage.He tried to pull the ruined fence back into place,but it wouldn't move.I looked out of the window,silently cheering.The man tried harder.However,suddenly,the man fell hard onto the ground with one of his shoes landing 10 feet away on the sidewalk.I think I laughed out loudly.That almost brightened my whole morning.He stood up and walked slowly to a nearby apartment.That,I thought,would be the end of it.The man was going to leave the mess behind for someone else to clean up.
However,a few minutes later the man appeared with some tools and for the next hour, I watched out of my window as he stubbornly fixed the fence.Now the fence would be extra secure,stronger than before.That man was actually a hero.My ugly assumptions(设想），I realized,were all about myself.I would never have fixed that fence and run away.
Years later I still look out of my window at the fence almost every day.It makes me wonder what else that man has improved and how I can make myself more like him.
1. In paragraph 2,the author thought of the man as______| A．irresponsible | B．impatient. |
| C．thoughtful | D．loving |
| A．the man's trying to fix the fence |
| B．the man's falling onto the ground |
| C．the man's car crashing into the fence |
| D．the man's kid running around cheerfully |
| A．The man left his shoes on the sidewalk. |
| B．The man protected his child from the car crash. |
| C．The man tried to put the damaged fence in place. |
| D．The man came back to fix and improve the fence. |
| A．No pains,no gains. |
| B．You can never be too careful. |
| C．Don't judge a book by its cover. |
| D．He who makes no mistakes makes nothing. |
【推荐2】Leaders in the aviation (航空) industry plan to launch a campaign (发起运动) that they hope will work against what they call a “Flight Shaming Movement” (FSM). They say FSM has weakened people’s demand for air travel in Europe. Some travelers there are increasingly concerned about the effects of flying on the environment. Activists have been calling for greater action against climate change. That includes avoiding air travel.
FSM has affected air travel demand in many European countries, including Britain, France and Germany. The campaign will try to explain to the public how the industry is reducing its effect on the environment. Juniac, head of IATA, said FSM gave off “misleading information”.
The International Air Transport Association (IATA) is organizing the plan through the Air Transport Action Group, a group of aviation industry organizations and companies. Juniac didn’t say when the campaign would start, but noted that details would be available to airports and airlines.
Commercial flying is estimated to cause about 2.5% of worldwide carbon emissions (释放). However, that number could rise as worldwide air travel increases.
The aviation industry says it has already cut carbon emissions by one-half since 1990. The improvements are mainly the result of aircraft that use fuel more effectively. The industry plans to cut emissions further by 2050. It has a goal of stopping the growth of carbon emissions by 2020.
Airlines also have warned of the harmful effects of FSM. Some have criticized the industry for failing to explain itself. Tim Clark, president of the Airline Emirates, said that improvements in technology have reduced the environmental effects of passenger airplanes.
1. What is FSM about?| A．Weakening people’s demand to travel abroad. |
| B．Calling on all to fight against global warming. |
| C．Announcing the environmental harm of flying. |
| D．Scaring people from approaching the airport. |
| A．Airlines will charge the movement for their loss. |
| B．It ignores the efforts of airlines to reduce pollution. |
| C．Airlines are to blame for the cause of it. |
| D．It has positive effects in urging airlines to be green. |
| A．The effective use of fuel has made air travel greener. |
| B．FSM has caused great loss for aviation industry. |
| C．With more passengers, carbon emissions by planes may rise. |
| D．The aviation industry aims to stop carbon emission by 2020. |
| A．Improvement of air quality since FSM. |
| B．Measures by aviation industry to reduce pollution. |
| C．Travelers’ inconvenience caused by FSM. |
| D．Disapproval of aviation industry against FSM. |
【推荐3】Imagine that you’re the creator and show runner of the newest comedy show on television. Only it isn’t so popular yet, and your live Studio audience isn’t giving you the big laughs the show deserves. Do you film the show all over again, hoping that this time the audience will laugh? Or is there another option for making a joke sound funnier than it was received?
Sweeten(改善) the sound by adding a laugh track! “Sweetening,” or the addition of sound effects such as laughs, screams, and other audience-produced noises to the audio track of a TV show, has been used since the 1940s to produce the appearance, or rather the sound, of an engaged and entertained response to a show’s comedy. Laugh tracks came into existence as not only a solution, and sometimes replacement, for an unengaged live audience but also as a way to engage an at-home audience into a more-traditional, public, and theaterlike experience. Adding a laugh track to a television show makes the viewers at home feel much less like they’re sitting on a couch staring at the television screen and much more like they’re in a room full of laughing happy people to varying degrees of success.
Though the art of sweetening has risen and fallen in popularity over the past 60 years, credit for its creation and continued use is owed to laugh-track pioneer and sound engineer Charles Douglass. Douglass was the first to develop, in 1953, a machine for producing “canned laughter”, accessible at the push of a button or pull of a lever (操纵杆). Despite being artificial, sensibly edited laugh tracks are found by television studios to bring about a positive audience response, as their use is usually accompanied by higher ratings and increased audience memory. Though some television audiences may disagree with the value of the laugh track, the cheerful and repetitive sound holds a permanent place in the history and future of television comedy.
1. The author uses the first paragraph to .| A．introduce the topic “sweetening” |
| B．seek solutions for the problem |
| C．point out a way of making comedies |
| D．arouse readers’ interest in comedies |
| A．The creation of a show. |
| B．Funnier sound in a show, |
| C．More engaged live audience |
| D．Communication among TV viewers. |
| A．Doubtful. | B．Positive. |
| C．Neutral (中立的). | D．Uncertain, |
| A．The reason for using laugh tracks. |
| B．The brief history of laugh tracks. |
| C．The development of TV comedies. |
| D．The way to improve television shows. |
【推荐1】Shopping is a big part of the holiday season,when families and friends gather together and exchange gifts.While the popularity of shopping online has grown,such practices are not always eco-friendly or timely,as gifts bought online must be packaged and shipped,wasting valuable resources and time.
The benefits of shopping locally go beyond convenience and reduce your carbon footprint.The following are a few ways that shopping locally this holiday season can directly benefit your community and the people who call it home.
When men and women shop locally,they are putting money back into their local communities.Local businesses may be owned by your neighbors,and it can be comforting to know that your holiday shopping dollars are going to support a neighbor instead of a large company.Local businesses also employ your neighbors,so shopping locally can strengthen the local economy by creating jobs.
Local businesses go a long way toward creating a neighborhood identity,and that identity can create a stronger sense of community among you and your neighbors.In addition,a unique community identity can make your town more attractive to outsiders,and can also attract more people to local businesses in your neighborhood.
The gifts you buy when shopping locally can also benefit your community.Gifts purchased from small local businesses tend to be more unique than items bought from national chains,as smaller retailers tend to sell more home-made items than their national competitors.Recipients of such items may find such gifts more thoughtful than mass produced items bought from national chains.
The accessibility of customer service is another benefit of shopping locally.When you buy something from national chains,especially during the holiday season when such businesses may have to deal with orders,making contact with customer service departments can be a test of patience.A long wait on the phone or online can make the process of contacting customer service departments extremely frustrating.But such frustration is rare when shopping from local businesses,as consumers can simply buy their products in the store.In addition,shopping locally makes it more convenient for friends and family members who also live in your community to return their gifts.
1. The author referred to shopping online in the passage to .| A．imply it is convenient to shop online |
| B．show it has been popular with the public |
| C．imply shopping locally is better than that |
| D．tell people they should stop wasting resources |
| A．local businesses are in poor management |
| B．shopping locally can help some people get jobs |
| C．a large company usually gains much profit |
| D．few people support local businesses |
| A．the business will raise the price of its products |
| B．the products will be sold in the distant places |
| C．it will help develop the community a lot |
| D．the community will turn into a tourist destination |
| A．The persons who receive something. |
| B．The persons who donate something. |
| C．The persons who sell something. |
| D．The persons who purchase something. |
【推荐2】Jerome Karie and Isabella Lugoski met in their first physical chemistry class at the University of Michigan in 1940. Jerome Karie was in his first year of doctoral work, Isabella Lugoski was in her last year as an undergraduate(大学本科生), and they were laboratory partners. However, they didn't get along well at first.
Isabella Lugoski looked back on the past, “I walked into the physical chemistry laboratory and there's a young man in the desk next to mine with his equipment all set up running his experiment. I don't think I was very polite about my question. I asked him how he got there early and had everything all set up. He didn't like that. So we didn't talk to each other for a while.
Their relationship got going as they competed for the top grade in that course and they started to build connection because both of them were interested in chemistry. They married in 1942. By 1946, both of the Karies had earned doctorates in physical chemistry, and, after a period of time at the University of Chicago working on the Manhattan Project, moved to Washington DC to join the US Naval Research Laboratory.
Each specialized in a different aspect of X-ray crystallography(晶体学): Jerome focused on developing equations(方程式) that could determine how atoms(原子) were arranged inside complex molecules, while Isabella ran practical experiments to test how well the equations worked. Working together, they created what is now called the direct method for determining molecular structures(分子结构), which has allowed scientists to effectively study and copy complex organic molecules to continue further study.
Jerome Karie was awarded the Nobel Prize for Chemistry in 1985. Although he was disappointed that the Nobel committee had ignored Isabella's contribution to that work, she was unfazed. At that point, she had already won more awards and prize money for her experimental work than he had.
1. What did Isabella Lugoski do when she first met Jerome Karie?| A．She blamed him for his being late. | B．She set up all his equipment for him. |
| C．She asked him a question impolitely. | D．She observed his experiment silently. |
| A．Their common interest in chemistry. | B．Their wonderful marriage since 1940. |
| C．Their pleasant first talk in a laboratory. | D．Their successful cooperation in courses. |
| A．The Karies' encouraging further study. | B．The Karies' good teamwork in science. |
| C．How the Karies worked with others. | D．Why the Karies won the Nobel Prize. |
| A．Generous. | B．Touched. | C．Shocked. | D．Calm. |
【推荐3】The Arctic's permafrost is inciting— and fast. That's bad news, because these frozen soils store billions of tons of carbon, just waiting to be released. So is there a way to save the permafrost? One team of researchers thinks it may have found a possible solution: big animals, herbivores - animals that eat only plants.
Back in 1996 researchers started an experiment called Pleistocene Park. They fenced in about eight square miles of land in northeast Siberia. Then they introduced different types of herbivores: reindeer, horses, bison, sheep and other large creatures.
Since then, scientists have studied these animals' effects on the ecosystem. One outcome is that these large herbivores help keep the ground very cold — cooler than it would otherwise be.
“The snow in winter is important for soil temperature, because it acts as an insulating layer. So the air in winter, at the high latitudes, is much colder than the soil." Philipp Porada, a vegetation ecologist at the University of Hamburg. "So the idea of this experiment was to introduce large herbivores — and to quantify their effects on soil temperature to see if they can actually protect permafrost soils against melting. And this works because of the animals' trampling (践踏), and this leads to less insulation of the soil against cold air temperatures and results in a cooling effect.”
Freezing air reaches the soil more easily. Porada and his colleagues realized the significance of this effect, so they pulled data from Pleistocene Park and Sweden to model what effect herbivores could have on permafrost if they lived in large numbers in the Arctic.
They found that even in a worst-case situation, some four degrees Celsius of global wanning: “These herbivores in the model reduce soil temperature substantially, by 1.7 degrees on average. And this leads to a preservation of around 80 percent of the original — today's permafrost area. Without the herbivore effect in the model, only 50 percent of the permafrost area would remain by the year 2100. So we can say the effect of the herbivores in the model leads to a substantial preservation of permafrost soil."
1. Why is the Pleistocene Park Experiment mentioned?| A．To provide the past research data. |
| B．To share soil preservation experience. |
| C．To introduce a way to save permafrost. |
| D．To prove animals' effect on soil temperature. |
| A．Covering. | B．Blocking. |
| C．Storing. | D．Freezing. |
| A．Cooling the ground. | B．Heating the soil |
| C．Damaging the ground. | D．Softening the soil. |
| A．Permafrost Is Disappearing | B．Preservation of Permafrost |
| C．An Experiment on Herbivores | D．Herbivores Help Save Permafrost |
