The combined quantity of water on Earth has varied over the course of our planet’s geological history, and it still does.
Today, Earth includes some 1,386 million cubic kilometres of water, a volume that includes water in oceans, lakes and rivers, plus ground water, vapour in the atmosphere, and the frozen water of glaciers and ice caps. On the young Earth — some four billion years ago — vast quantities of water were added to the planet by ice-containing comets (a mass of ice and dust that moves around the sun and looks like a bright star with a tail) that struck us, eventually making our world a “blue planet”. But such events became increasingly rare in Earth’s more recent history, and today we are in an age during which Earth is losing water.
The water loss is due to the fact that particles (微粒) sometimes escape Earth’s gravity to travel into space. This is particularly true of the light hydrogen atoms that form part of water molecules (分子) together with oxygen. Every time the atmosphere loses hydrogen, we lose one of the building blocks of water. Scientists estimate that Earth loses about 3kg of hydrogen per second. At this pace, Earth would run out of water in three billion years — but that assumes that we don’t get any new water supplies.
New water need not come from space — it might come from the inside of the Earth. At depths below 50km, minerals contain water that is not reckoned within the water cycle. Some of it dates back to Earth’s formation; the rest is part of slow geological exchange between the planet’s layers. When Earth’s plates sink and melt, deep minerals can release these bound water molecules so that they can subsequently rise to the surface via volcanic eruptions, adding to the planet’s overall water resources.
1. How did Earth become a “blue planet” in geological time?| A．By getting water from comets | B．By making use of glaciers. |
| C．By releasing its inside water. | D．By storing water in the ocean. |
| A．Serious. | B．Regretful. | C．Uncertain. | D．Unworried. |
| A．locked | B．displayed | C．counted | D．marked |
| A．Where Can Water Be Stored? | B．Could Earth Run Out of Water? |
| C．How Can New Water Be Found? | D．Will There Be More Water on Earth? |
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【推荐1】This summer, NASA launched its latest robot Perseverance on a seventh-month journey to Mars. During the past decades, robot explorers on Mars have made great discoveries about the red planet, but they have never found clear-cut signs of creatures currently living there. Life, at least as we know it on Earth, simply does not seem probable on the Martian surface.
“If there’s any life on Mars now, it needs at least some liquid water,” Dr. Sumner said. “The surface of Mars now is very dry. Extremely dry. If there’s life on Mars now, it would be found deep underground.” Actually, there has been some evidence that liquid water is locked away beneath the surface, so perhaps there are sunless ecosystems hidden there, which are beyond the direct reach of our rovers and landers.
“Recent findings of methane and other gases in what’s left of Mars’ atmosphere are a potential signature,” Dr. Farley said, supporting the theory about underground water. Many microbes on Earth produce methane, so it is possible that the gas on Mars could be related to alien life-forms deep underground.
However, methane can also be created by a wide range of natural processes that have nothing to do with life. Some experts, like Dr. Sumner from the University of California Davis, say that the presence of the gas on Mars is “not a surprise” because it has all the geological processes it needs to produce the gas without life.
But even if we never find Martians, “Mars is a place we can go to answer some of the questions about life on Earth,” Dr. Sumner said. The red planet remains a time capsule of the era when life first began on our own world, and the direction it could have gone had all the factors that made our world possible, yet it turned out just not the right way.
1. Where can life on Mars possibly be?| A．In the methane. | B．On the surface. |
| C．In the underground. | D．In the atmosphere. |
| A．It proves the existence of microbes on Mars. |
| B．Some forms of life on Earth can produce the gas. |
| C．Underground water has something to do with the gas. |
| D．It shows different kinds of gas exist in the air on Mars. |
| A．Methane doesn’t actually exist on Mars. |
| B．Methane is a necessary condition of life. |
| C．Scientists have predicted the existence of methane. |
| D．The discovery of methane doesn’t guarantee life on Mars. |
| A．Arguments about life on Mars. | B．The value of exploring Mars. |
| C．NASA’s new robot on Mars. | D．Discovery of water on Mars. |
【推荐2】The moon’s gravity constantly pulls at the Earth. Its pull on the ocean is undeniable but some scientists have been studying less visible effects, which may be able to trigger some earthquakes, if the time is right. With the appearance of bigger and more complete dataset, this effect of the moon has started to show from the data. And it seems that in some cases, the moon did help trigger earthquakes around the world. With these huge databasets, they started to get some small but significant correlation. Chris Scholtz, a geologist and professor at Columbia Climate School, said, one place where the moon’s impact is seen clearly is in underwater earthquakes. That makes sense, given the moon’s pull on the oceans.
Scholtz and his team set out to study how the moon could be using its power on the earthquakes on the Axial Volcano. Earthquakes here are about tenfold more likely to happen when the tide has gone out. Their study found an explanation for the link between the moon and earthquakes. It showed they were caused by the weight of the ocean pressing down on a volcano’s magma chamber. Then when the tide is low, less water presses down on the chamber. This, in turn, puts more pressure on the fault-line, making it more likely to move and create an earthquake.
It’s not just in the oceans where the moon is causing disaster. The moon also causes tiny, but important, tides in rocks. “While fluids can flow, rocks can just slightly change their shape by the tidal force which promotes stress accumulation,” said Scholtz. If rocks are already over-stressed, even a small stress — the pull of the moon — can create a crack in the rock. “If surrounding rocks are also unstable, the fracture can speed up to involve large fault patches. The final outcome is an earthquake,” said Scholtz. Of course, this only happens in very specific circumstances, for instance, when the pressure from the moon’s gravitation al pull lines up perfectly with the fault-line of the earthquakes.
1. What has long been recognized as the moon’s effect on the earth?| A．Earthquake. | B．Tide. | C．Volcanic eruption. | D．Hurricane. |
| A．Big data. | B．Their team cooperation. |
| C．His initial guess. | D．Previous research results. |
| A．By pulling on the oceans of the earth. | B．By applying invisible force to the earth. |
| C．By changing the earth’s physical structure. | D．By putting pressure on the fault-lines of the earth. |
| A．The Moon — The Decisive Factor for Earthquakes |
| B．The Tides — The Moon’s Constant Pull at the Earth |
| C．The Gravity — A Hidden Trigger behind Earthquakes |
| D．The Earthquake — A Frightening Result from Over-stressed Rocks |
【推荐3】Back in 2015 my colleague Adam Frank of the University of Rochester and I were having lunch near Columbia University's campus in New York City. As at Fermi's lunch 65 years earlier, the conversation was about the nature of spacefaring species. And inspired by Fermi's mental calculation, we were trying to craft an investigative strategy that made the fewest possible unsubstantiated assumptions and that could be somehow tested or constrained with real data. At the center of this exercise was the simple thought that waves of exploration or settlement could come and go across the galaxy, with humans happening to come into being in one of the lonely periods.
This idea relates to Hart's original fact: that there is no evidence here on Earth today of extraterrestrial（外星的）explorers. But it goes further by asking whether we can obtain meaningful limits on galactic（星系的）life by constraining the exact length of time over which Earth might have gone unvisited. Perhaps long, long ago extraterrestrial explorers came and went. A number of scientists have, over the years, discussed the possibility of looking for artifacts that might have been left behind after such visitations of our solar system. The necessary scope of a complete search is hard to predict, but the situation on Earth alone turns out to be a bit more manageable. In 2018 another of my colleagues, Gavin Schmidt of NASA's Goddard Institute for Space Studies, together with Adam Frank, produced a critical assessment of whether we could even tell if there had been an earlier industrial civilization on our planet.
As fantastic as it may seem, Schmidt and Frank argue—as do most planetary scientists—that it is actually very easy for time to erase essentially all signs of technological life on Earth. The only real evidence after a million or more years would boil down to isotopic or chemical stratigraphic anomalies—odd features such as synthetic molecules, plastics or radioactive fallout. Fossil remains and other paleontological markers are so rare that they might not tell us anything in this case.
Indeed, modern human urbanization covers only on order of about 1 percent of the planetary surface, providing a very small target area for any paleontologists（古生物学家）in the distant future. Schmidt and Frank also conclude that nobody has yet performed the necessary experiments to look exhaustively for such non-natural signatures on Earth. The bottom line is, if an industrial civilization on the scale of our own had existed a few million years ago, we might not know about it. That absolutely does not mean one existed; it indicates only that the possibility cannot be completely eliminated.
1. The word “unsubstantiated”（in paragraph 1）is closest in meaning to ________.| A．unconscious | B．unknown | C．unnatural | D．unsupported |
| A．No other species have ever settled on Earth except human beings. |
| B．Extraterrestrial explorers come and go at increasingly short intervals. |
| C．No spacefaring species have visited the Earth since humans emerged. |
| D．Extraterrestrial explorers once built an industrial civilization on Earth. |
| A．turn to isotopic or chemical stratigraphic anomalies |
| B．find as many signs of technological life as possible |
| C．unearth more fossil remains than we do now |
| D．leave behind synthetic things like plastics |
| A．Human urbanization should be expanded for the sake of research. |
| B．We cannot say for sure that no civilization existed before ours. |
| C．Non-natural signatures on Earth have been studied exhaustively. |
| D．An industrial civilization came into being a few million years ago. |
While many of us go through life with the pursuit of money on our mind, we’re often told that money can’t buy happiness. But what truth is there in the saying? Is there a relation between money and happiness?
Humans are very sensitive to change. When we get a rise, we really enjoy it. But some studies have shown that in North America, additional income beyond 75,000 dollars a year stops impacting day-to-day happiness.
So surely money can’t really buy happiness. Well, recent studies suggest that the problem may actually be in the way that we spend money.
| A．The same principle has been tested on teams and organizations as well. |
| B．Money has more effect on the vast majority of people in the long run. |
| C．Instead of buying things for yourself, try giving some of it to other people and see how you feel. |
| D．And if so, how can we use it to our advantage? |
| E．Almost everywhere we look in the world, we see that giving money to others is positively related to happiness. |
| F．And while you’re saving up for these greatest experiences, don’t forget the daily joys in life. |
| G．In fact, people who win a lottery often report becoming extremely unhappy. |
【推荐2】Have you ever noticed that some people can eat what they want and stay in shape, while others carefully watch what they eat and still put on weight? How annoying! However, scientists are beginning to believe that some people get the ability to stay thin from their parents.
Scientists say that when some people eat, their bodies will naturally store the excess energy from food as fat. These people gain weight if they eat more than they need each day. Meanwhile, other people eat more than they need but their bodies are able to “burn off” the extra food without making fat, so they rarely have weight problems.
To show that this is true, scientists have experimented on laboratory mice. They gave the mice a special diet with a lot of fat. Some mice gained weight while the other mice stayed thin, even though both groups of mice ate the same amount of food and got the same amount of exercise. Scientists concluded that weight gain seemed to be influenced by genetic (基因的) factors. They also believe they have now identified the genes that may cause this tendency. These genes, according to the scientists, get passed down the generations. Armed with this knowledge, they believe it may be possible to develop medicines that can target the genes and stop people from gaining weight.
The study of weight gain is becoming more important as the numbers of people who are overweight continues to grow. In the United States, over seventy percent of the population have weight problems. This means they are at risk of illness such as high blood pressure and heart disease.
Current medicines for weight control do not work very well because they can have serious side effects, such as heart problems. However, it takes a long time to develop and thoroughly test new drugs. Therefore, despite this breakthrough in the study of weight-loss drugs, scientists and health professionals all agree that currently the best way to control weight gain is to have a healthy, balanced diet and an active lifestyle with daily exercise. This will not only help people avoid becoming overweight, but also help them stay healthy and energetic.
1. According to the scientists, some people ________.| A．are able to stay thin because of genetic factors |
| B．can eat what they want and stay healthy forever |
| C．usually keep doing exercise to lose their weight |
| D．don’t eat anything every day but still put on weight |
| A．they eat many vegetables |
| B．they eat less than others |
| C．they don’t store any energy from food as fat |
| D．they can burn off the extra food without making fat |
| A．Fewer people will have weight problems in the future. |
| B．People with weight problems may suffer from heart trouble. |
| C．We now have good medicine for people with weight problems. |
| D．The result of the experiments on mice and humans are different. |
| A．Current medicine solve weight problems well. |
| B．We should exercise regularly and eat properly. |
| C．Taking exercise every day may cause heart problems. |
| D．Testing new drugs is hard because of the side effects. |
【推荐3】Fossils discovered in Liaoning province have challenged the theory that the Archaeopteryx is the earliest known bird.
Research of the fossils led by Pascal Godefroit and his team from the Royal Belgian Institute of Natural Sciences revealed that the dinosaur bird Aurornis xui, like the Archaeopteryx, existed nearly 150 million years ago. Godefroit told British-based Daily Mail, “The evolutionary development shows that dinosaur birds were already diversified in northern China during the Middle-Late Jurassic.”
The study, published in the journal Nature, showed that Aurornis xui was 50 cm in length and had tiny teeth used for hunting and defense, similar to other dinosaurs. Godefroit said the results support a “single origin of powered flight”, which suggests that all dinosaurs that became birds took flight around the same time, and eventually lost hunting and defensive features, like teeth, during adaptation.
Hu Dongyu, a professor at Shenyang Normal University, pointed out that fossils of some dinosaurs show that the legs initially had long feathers, which suggests they assisted wings in flight. “But the long feathers on the legs degenerated as the wings became strong enough. This is not the first time that fossil evidence has showed the evolution path from dinosaurs to birds,” said Hu. “The initial question was whether these dinosaur birds existed before the Archaeopteryx, but as we dig deeper into them, the age became irrelevant. And now the bone of contention is whether all these dinosaur birds are dinosaurs or birds.”
One fossil, found in Liaoning in 2009 and studied by scientists led by Xu Xing from the Chinese Academy of Sciences in Beijing, showed that the earliest dinosaur bird was Anchiornis huxleyi, a flying dinosaur that lived 160 million years ago. Another fossil studied by Xu and his colleagues, also believed to be a dinosaur bird, was named Xiaotingia zhengi. “Aurornis xui, Anchiornis huxleyi and Xiaotingia zhengi are similar dinosaur bird fossils,” Hu added. “The earlier research suggested that all dinosaur birds were dinosaurs, not birds. However, recent research suggests the opposite. So there is a long way to go to draw a conclusion.”
1. What is the topic of the text?| A．The origin of birds. | B．The adaptability of birds. |
| C．The time when dinosaurs appeared. | D．The reason why dinosaurs died out. |
| A．The speed of its flight. | B．The force of its defense. |
| C．The length of its feathers. | D．The feature of its teeth. |
| A．The bones of birds. | B．The focus of debate. |
| C．The similarity of theories. | D．The conclusion of research. |
| A．They were dinosaurs. | B．They need further study. |
| C．They could fly like birds. | D．They existed before the Archaeopteryx. |
【推荐1】Chinese Paper Cutting or Jianzhi is the first type of paper-cutting design, since paper was invented in China during the Eastern Han Dynasty.
It’s a unique visual art of Chinese handicrafts. The art form later spread to other parts of the world with different areas adopting their own cultural styles. After hundreds of years’ development, now they’ve become a very popular means of decoration among country folks, especially women. The paper-cuts are also used to decorate doors and windows, and therefore they are sometimes referred to as “chuang hua”, meaning window flowers. Paper-cuts are chiefly used as decorations. However, today, Chinese paper-cuts are also used for religious and ceremonial purposes, and they’re buried with the dead and burned at funerals.
Chinese people believe the red paper-cuts on the door can bring good fortune and happiness to the whole family. The paper-cuts are more often seen during traditional Chinese festivals, particularly in Chinese New Year, the Spring Festival. They’re also given as gifts to friends or other family members.
Paper-cuttings aren’t produced by machine, but by hand. There’re two methods of manufacture: one uses scissors, the other uses knives. Knife cuttings are fashioned by putting several layers of paper on a relatively soft foundation. Following a pattern, the artist cuts the motif into the paper with a sharp knife he usually holds vertically (垂直地). The advantage of knife-cutting is that considerably more paper cuttings can be made in one operation than with scissor cuttings.
It’s easy to learn about cutting a piece of paper but difficult to master it with perfection. One must grasp the knife in an upright fashion and press evenly on the paper with some strength. Flexibility is required but any hesitation will damage the whole image.
People find hope and comfort in expressing wishes with paper-cutting. For instance, for a wedding ceremony, red paper-cuttings are a traditional decoration on the tea set, the dressing table glass, and on other furniture. A big red paper character “Xi” (happiness) is a traditional must on the newly-wed’s (新婚夫妇) door.
1. What can we learn about paper-cuts?| A．They vary from area to area. | B．They were invented by females. |
| C．They are mainly used as presents. | D．They can’t be used in funerals. |
| A．Line. | B．Pattern. | C．Photo. | D．Foundation. |
| A．The type of knives. | B．The knife skill. |
| C．The amount of paper. | D．The quality of paper. |
| A．Paper-cutting: Chinese Folk Art |
| B．Paper-cutting: Famous in China |
| C．Paper-cuts: Various in Different Culture |
| D．Paper-cuts: Widely Used in Ceremonies |
【推荐2】Robots can deliver food on a college campus and hit a hole in one on the golf course, but even the most advanced robot can’t perform basic social interactions that are vital to everyday human life.
MIT researchers have now added certain social interactions to a framework for robotics, enabling machines to understand what it means to help or hinder (阻碍) one another, and to learn to perform these social behaviors on their own. In a simulated (模拟的) environment, a robot watches its companion, guesses what task it wants to accomplish, and then helps or hinders the other robot based on its own goals. The researchers also showed that their model creates realistic and predictable social interactions. When they showed videos of these simulated robots interacting with one another to humans, the human viewers mostly agreed with the model about what type of social behavior was occurring.
Equipping robots with social skills could lead to smoother and more positive human-robot interactions. For instance, a robot in a nursing home could use these abilities to help create a more caring environment for elderly individuals. The new model may also enable scientists to measure social interactions quantitatively (数量上), which could help psychologists study autism (自闭症) or analyze the effects of antidepressants (抗抑郁药).
“Robots will live in our world soon enough and they really need to learn how to communicate with us on human terms. They need to understand when it is time for them to help and when it is time for them to see what they can do to prevent something from happening. This is very early work and we are barely scratching the surface, but I feel like this is the first very serious attempt for understanding what it means for humans and machines to interact socially,” says Boris Katz, leading research scientist.
1. What can robots in use at present do?| A．Talk with humans freely. |
| B．Measure social interactions. |
| C．Perform various social skills. |
| D．Accomplish basic instructed tasks. |
| A．Opinions about robots having social skills. |
| B．Ways of developing robots’ social skills. |
| C．Significance of developing robots’ social skills. |
| D．Purposes of equipping robots with social skills. |
| A．Challenging but promising. |
| B．Shallow and time-consuming. |
| C．Successful but old-fashioned. |
| D．Urgent and accurate. |
| A．Future Robots on Campus | B．Giving Robots Social Skills |
| C．New Research into Robots | D．Linking Robots and Humans |
【推荐3】Ever since the 2012 publication of Cheryl Strayed’s best-selling book, Wild, which records her 1100-mile hike along the Pacific Crest Trail from California to Washington state all by herself, many more people have been preparing their hiking shoes.
Hiking is now the fourth most-popular outdoor activity in the U.S., after running, fishing and biking, according to The Outdoor Foundation’s 2018 Outdoor Participation Report. The report noted that 44.9 million people hit the trails (步道) in 2017, up from 30 million in 2006. The biggest jump in participation came between 2015 and 2016.
Trimble, a government official, says in addition to the “Wild” effect, he believes hiking is increasing in popularity because more people are discovering the nation’s various trail systems and learning about the concept of long-distance hiking. “I also think the Millennials, and even Generation Z, are putting a lot more value on experiences than on money and career advancement,” he says. “Cultural changes have played a role in the number of people getting out on the trails.”
Mike Wollmer is a director of the Ice Age Trail Alliance (IATA), which protects, keeps and advocates for the Ice Age Trail, another one of the 11 National Scenic Trails. Wollmer believes social media has also helped to improve hiking numbers, as it is being used to show the beauty and diversity of U.S. hiking trails, construction projects and more. This is especially true for less famous paths such as the Ice Age Trail, which winds 1150 miles around Wisconsin, presenting the state’s Ice Age landscapes (风景).
The IATA recorded 76 trail completions between the path’s birth in the 1970s and 2012. During the next six years, another 114 people reported trail finishes. The hiking community also created the IATA-specific “Thousand Miler Wanna Bes” Facebook page, aimed at helping people achieve their dream of becoming a “thousand-miler”, a special title the IATA gives to those who have completed the entire trail.
1. Why was the book Wild mentioned in the beginning?| A．To lead to the topic of the text. | B．To recommend an influential book. |
| C．To analyze the popularity of the book. | D．To introduce the beautiful wild of the US. |
| A．The book Wild. | B．The social media. |
| C．The desire to get experiences. | D．The state’s Ice Age landscapes. |
| A．An honor. | B．A Facebook page. |
| C．A sum of money. | D．A landscape picture. |
| A．Hiking, Hiking, Hiking | B．Why Hiking Is Increasing in the USA? |
| C．American Outdoor Activities Are Improving | D．Do You Know American Trails? |
