SpaceX will soon have a whole fleet of shiny silver Starship prototypes(原型), if all goes according to the plan. Elon Musk gave his annual update about Starship and Super Heavy, the reusable spaceship and rocket, respectively, that the company is building to help colonize Mars. The presentation took place at SpaceX s South Texas site and featured the 165-foot-tall Starship Mkl- the first full-size Starship prototype, whose assembly(组装) was completed just days before Musk's talk.
SpaceX aims to launch the stainless-steel Mk1 on an uncrewed, 12- mile- high test flight in the next month or two, Musk said. And a much more ambitious journey should follow in relatively short order. “I mean, this is going to sound totally unrealistic, but I think we want to try to reach orbit in less than six months.” But the Mk1 won't make that milestone flight. That honour will be likely to go to Mk4 or Mk5 Starship version, Musk added.
Starship Mk2 is already under construction and should be finished within the next couple of months at most. SpaceX plans to begin building the Mk3 at Boca Chica in about a month, and that prototype will likely be ready to fly about three months from now. The Mk4 will take shape in Florida shortly after that- and it could end up being the first Starship vehicle to circle Earth.
Like most of Musk' s plans, these construction schedules are quite ambitious. SpaceX spent a lot of time on the Mk1, after all; construction work on that vehicle goes all the way back to at least December 2018. But the company has learned a lot during the time, so getting a Starship to orbit by the spring of 2020 should be achievable, Must said.
The Mk1 and Mk2 Starships are equipped with three of SpaceX’s next- generation Raptor engines. Versions starting with Mk3, however, will be powered by six Raptors, just like the final, operational Starship, which Musk has said will be capable of carrying up to 100 passengers.
At present SpaceX is building one Raptor every eight to ten days but should pick up the pace obviously in the coming months. The record will skyrocket when SpaceX starts building the Super Heavy, which won't happen until Starship Mk4 is done. The goal is to get to one Raptor per day by early 2020 at the latest.
The final Starship could take to the skies very soon, if the testing campaign continues to go well. And Japanese billionaire Yusaku Maezawa has booked a crewed flight around the moon aboard the system, with a target launch date of 2023.
1. What can we learn about the Starship Mk1?| A．It is an imaginary passenger-carrying vehicle. |
| B．It is an unmanned reusable large spaceship. |
| C．It is a scaled-down version of Super Heavy. |
| D．It is a stainless-steel spaceship under construction. |
| A．By three of SpaceX's next generation Raptor engines. |
| B．By four of SpaceX' s next- generation Raptor engines. |
| C．By five of SpaceX's next- generation Raptor engines. |
| D．By six of SpaceX s next- generation Raptor engines. |
| A．It will take up to 100 passengers to space. |
| B．It is the first to make a test flight orbiting Mars. |
| C．It has been under construction for about one year. |
| D．It is expected to go into Earth's orbit before long. |
| A．The project of SpaceX is promising. |
| B．Space exploration has caught on worldwide. |
| C．SpaceX takes the lead in the aerospace field. |
| D．More financial support is desperately needed. |
相似题推荐
【推荐1】Something in chocolate could be used to stop coughs and lead to more effective medicines, say UK researchers.
Their study found that theobromine, found in cocoa, was nearly a third more effective in stopping coughs than codeine, which was considered the best cough medicine at present.
The Imperial College London researchers who published their results online said the discovery could lead to more effective cough treatment. “While coughing is not necessarily harmful, it can have a major effect on the quality of life, and this discovery could be a huge step forward in treating this problem,” said Professor Peter Barnes.
Ten healthy volunteers were given theobromine, codeine or placebo, a pill that contains no medicine, during the experiment. Neither the volunteers nor the researchers knew who received which pill. The researchers then measured levels of capsaicin, which is used in research to cause coughing and as a sign of how well the medicine are stopping coughs.
The team found that, when the volunteers were given theobromine, the capsaicin need to produce a cough was around a third higher than in the placebo group. When they were given codeine they need only slightly higher levers of capsaicin to cause a cough compared with the placebo.
The researchers said that theobromine worked by keeping down a verve activity(神经活动), which cause coughing. They also found that unlike some standard cough treatments, theobromine caused no side effects such as sleepiness.
1. According to Professor Barnes, theobromine ______.| A．cannot be as effective as codeine | B．can be a more effective cure for coughs |
| C．cannot be separated from chocolate | D．can be harmful to people’s health |
| A．Capsaicin. | B．Codeine. |
| C．Theobromine. | D．Placebo. |
| A．were patients with bad coughs | B．suffered little side effects |
| C．received standard treatments | D．were divided into the three groups |
| A．Codeine: A New Medicine | B．Cough Treatment: A Hard Case |
| C．Chocolate May Cure Coughs | D．Theobromine Can Cause Coughs |
【推荐2】Alex Vardakostas spent his childhood flipping (快速翻转) burgers at his parents’ restaurant in Southern California. It was, he recalls, a repetitive and uninteresting task.
Vardakostas said, “Making so many burgers every day, I realized that there must be a better product I can create to make food.” He helped develop the restaurant’s main attraction: a robot machine that makes “the world’s freshest cheeseburgers.”
The machine has already drawn big crowds. People want to see exactly how a robot makes a burger and whether it tastes good. The robot is 14-feet long and takes five minutes to make a burger from start to finish.
After seeing the robot in action, one customer, Evan, was almost speechless. “I knew that they could drive cars,” he said, “but I didn’t know that robots could make a complex delicious burger.”
The robot’s 350 sensors and 20 microcomputers help make sure that every burger is perfect. The materials are organic and locally sourced whenever possible, but the burgers are still affordable. Because a machine makes the burgers, the restaurant doesn’t have to pay kitchen staff. Employees focus on offering the customers good service.
Besides, the restaurant offers its employees higher pay than the ordinary standard in the food industry. Staff members are able to read books for five percent of their workday so that they can continue to learn. Money is allotted for books, and more educational opportunities are being planned.
For Evan, the most important thing is still the burger. “The restaurant’s is the perfect chef,” he said, “because a person can make mistakes but a robot can’t.”
1. More and more customers visit Alex’s restaurant to ________.| A．eat the cheapest cheeseburgers | B．experience food made by a robot |
| C．watch how Alex flips burgers | D．learn from a robot to make food |
| A．Boring. | B．Interesting | C．Respectful | D．Surprising. |
| A．They aren’t sold at a high price. |
| B．Each of them owns an ugly shape. |
| C．They are equipped with sensors. |
| D．They become popular with the people around the world. |
| A．can become rich in a short time | B．need to buy books for customers |
| C．have to hand in their learning plans | D．can improve themselves by reading |
【推荐3】Over the past few years, cars have become smarter and smarter. Some of them can even drive themselves. Now, our roads have followed suit （跟着做）. In the United Kingdom alone, there are around 650 kilometers of “smart roads” in use. Across the world, many more are being built. Some new technologies are being put to use.
Roads that recharge（充电）
Global warming has made us search for new energy sources. Why not look to the roads? With the right technologies, cars around the world could be producing energy as they go. Piezoelectricity ads mix traditional asphalt（柏油）with new material. They use vibrations（振动）from passing cars to produce electricity. In fact, piezoelectricity is nothing new. It was invented in 1880. However, it has never been widely used before now. The UK’s Lancaster University is going to change that. It has been improving the technology, including developing roadside batteries that can store the electricity.
Roads that never freeze
________ A tech company in Israel has developed the Snowless roads. When they detect snow or ice on their surfaces, the roads will heat themselves up, melting the snow or ice away. The project has been successfully tested on a few Canadian roads and in some of its car parks.
Built-in brain
Roads of the future may be able to know how many people are on them. They could send them updates（实时信息）on weather and traffic jams, and recharge electric cars as they drive. This seems to be a dream, but one American company has almost made it come true. By sensing the weight of a vehicle, the company’s smart roads can track（跟踪）the speed of each wheel. “We are basically making very large touchpads,” says Tim Sylvester, CEO of the company. “but instead of looking for fingers, our roads look for tires.” After having collected traffic data, the roads will send it to the drivers.
1. According to the passage, “smart roads” ________.| A．haven’t been developed yet | B．have made cars drive themselves |
| C．have been widely built before | D．have been used in some countries |
| A．Many people like to drive smart cars. |
| B．This kind of roads can be frozen in winter. |
| C．It can be dangerous to drive in snowy weather |
| D．To change the common ways of driving is necessary. |
| A．how the roads work | B．what the roads can do |
| C．how large the roads are | D．how hard they work |
| A．The UK’s Lancaster University invented piezoelectricity. |
| B．Tim Sylvester’s company has made the large touchpads to track tires. |
| C．The Snowless Roads have been developed by a tech company in Israel. |
| D．One American company has built roads that could store electricity by themselves. |
【推荐1】Starship Technologies was founded in Estonia but is now based in San Francisco. The company employs dozens of six-wheeled delivery robots on college campuses. Now, Starship is adding four new schools to its operational field: University of Illinois Chicago, University of Kentucky, University of Nevada, Reno and Embry-Riddle Aeronautical University.
At present, the company operates on 20 college campuses in 15 states with a global fleet that totals 1,000 robots. This expansion will add 85 more robots to that fleet. Starship states that it has done over 5 million deliveries worldwide since its founding in 2014. The company has raised $ 102 million so far, including $ 17 million in fresh funding announced earlier this year.
Each robot in Starship is electric, has a box that can fit about 20 pounds of goods, and has a number of cameras to recognize obstacles and help guide it to its destination. The robots have a delivery range of three to four miles and can travel at a maximum speed of 4mph; which is obviously slower than a delivery by a human on a bike or in a car. And they can climb the edge of the road but not stairs, which may limit their appeal to customers who live in high-rise buildings.
Delivery via robots is still relatively neoteric in the US. There are a handful of start-ups operating delivery robots of varying sizes — everything from fully-sized minivans like Udelv to robots that are almost similar to Starship’s like Amazon and Yandex. Recently, Postmates has also invented a delivery robot called Serve that can carry 50 pounds of goods. There are even some newly-produced robots like Nuro, which can be described as a mini-robotic car. All claim to be automated, but some still require humans to follow their movements.
Demand for delivery robots has risen since the pandemic, though it remains to be seen whether that will hold up as the economy reopens and fewer people rely on takeout food from restaurants.
1. What can we learn about Starship Technologies?| A．It is now based in Estonia. | B．It hires college students as delivery men. |
| C．It is branching out into scientific education. | D．It is spreading its service on college campuses. |
| A．Modern people tend to rely heavily on robots. |
| B．Robots are popular among college students. |
| C．Starship has contributed a lot of money to charity. |
| D．Starship has made some achievements in robot delivery. |
| A．They work much slower than humans. | B．They are unable to recognize floors. |
| C．They have difficulty going up stairs. | D．They are likely to get lost in the buildings. |
| A．Novel. | B．Practical. | C．Traditional. | D．Necessary. |
【推荐2】Climate change has been a long-standing issue that continuously drives scientists to find green, sustainable fuels. The universe’s most abundant element, hydrogen (氢), has drawn their attention and is now on its way to becoming the future of green fuel.
More than $150 billion worth of green hydrogen projects were announced globally in 2020, according to Reuters. Airbus, a European multinational aerospace corporation, has taken the lead in the new sustainable fuel industry. It has designed self-contained hydrogen fuel cell pods that can be attached to the underside of airplane wings, promoting the use of hydrogen fuel for long-distance flights, which aim to achieve zero emissions. The company plans to launch hydrogen-powered aircraft in 2035, according to Daily Mail.
Compared to fossil fuels, hydrogen is a much more eco-friendly fuel. When hydrogen burns, the only by-product is water. However, the traditional way to get hydrogen from natural gas or coal generates considerable carbon emissions. The greenest way is to obtain hydrogen from water using electrolysis (电解) powered by renewable energy, although this process requires so much electricity that it is quite expensive. The key to making hydrogen competitive with fossil fuels is to lower the production cost to under $1.50. This would require lowering around 50 percent of renewable power costs and 75 percent of electrolyzer costs, according to Australia’s renewable energy agency.
Also, shipping liquid hydrogen is challenging, given that needs to be chilled to -253℃ to do so. Japan’s Kawasaki Heavy Industries is set to complete the construction of the world’s first liquefied hydrogen carrier by early 2021. According to Reuters, most of the world’s big hydrogen export projects are looking to ship hydrogen in the form of liquid ammonia (氨), which can be changed to hydrogen and needs to be chilled to only -33 C.
With more and more countries aiming to cut down carbon emissions to solve the issue of global warming, green hydrogen will help decarbonizing industries that can’t be electrified hit the targets.
“We could use these circumstances, where loads of public money are going to be needed into the energy system, to jump forward towards a hydrogen economy,” said Diederik Samsom, who heads the European Commission’s climate cabinet.
1. What is the strength of the hydrogen fuel?| A．It works very efficiently. | B．It is convenient to store. |
| C．It is environmentally friendly. | D．It produces no by-product. |
| A．The expensive cost of shipping. | B．The required temperature. |
| C．The construction of liquefied carriers. | D．Changing it to the form of liquid ammonia. |
| A．Those powered by fossil fuels. | B．Those generating electricity. |
| C．Those funded by public money. | D．Those making hydrogen. |
| A．Fueling a Green Future | B．Living a Green Life. |
| C．Shipping Liquid Hydrogen | D．Making Hydrogen Competitive |
【推荐3】Have you ever imagined what technology might look like in the future? Everything becomes easier, which is one tap. Over the course of human history, technology gradually can become so convenient and more than. And because of that, technology has been a large part of human life in the past 20 years. Educators also use technology to teach children about the use of technology in the current time.
Is that everything technology can do with education today? If you ask me, I would say parents who should be closest to their children should also use these wonderful tools in families’ education too. So why do I mention family’s education here and what does technology do with it?
Many people, especially parents, think they shouldn’t let their children interact with social network at this age. Don’t you think they are too young for it ?They may fall, they may become addicted to it, and not care about their parents anymore. And that’s why technology becomes used widely in many places, like schools and companies, but not in families. However, technology does carry many risks, and if you don’t know how to use and understand this probably it can easily lead to many disadvantages, especially for children, because they may not be aware enough of these dangers.
But fortunately, the disadvantages are avoidable. Families could set logical time to limit the children to use their electronic devices. Parents can also apply technology to teaching their children, so that games and videos are suitable for children with a certain amount of time.
Through technology, children can have more opportunities and more time to explore and develop themselves, and understand what they really like and find the true path in the future. These are things that often in school, children don’t get much access to because they have to spend more time on other subjects, like social science and maths. That’s why this is a good choice for parents to use technology to help children discover themselves at home.
1. What can we infer about technology from Paragraph 1?| A．It can provide more changes in history. | B．It becomes inconvenient and more than. |
| C．It can be difficult for people to acquire. | D．It plays an important role in daily life. |
| A．It is not easy to connect the Internet in families. |
| B．It is difficult to get access to technology in families. |
| C．Parents worry that it has a bad effect on children. |
| D．Children can’t get much amusement from technology. |
| A．Make the Internet offline. | B．Interact with social network. |
| C．Limit the time online. | D．Improve computer system. |
| A．Doubtful. | B．Negative. | C．Indifferent. | D．Favorable. |
【推荐1】Mangroves typically grow in saltwater along coasts. But some mangroves live in freshwater along the San Pedro Mártir River of Mexico's Yucatán Peninsula. That's nearly 200 kilometers from the sea. Scientists wanted to know how these mangroves got trapped so far inland.
Carlos Burelo was among them. He became curious about these mangroves on a childhood fishing trip. there with his dad 35 years ago. Burelo saw that the roots of the mangroves grew above ground. This was different from the other trees, and it interested him so much. Today, Burelo works at Universidad Juárez Autónoma de Tabasco, Mexico. This biologist is part of a team that went on to discover where those mangroves came from.
Burelo's team first collected leaves from these mangroves. The scientists then compared their DNA to those of leaves from coastal mangroves. The coastal trees were growing along the Caribbean Sea and Gulf of Mexico. The DNA helped find the origins of the mangroves on the San Pedro Marir River. They had started along the Gulf of Mexico, some 170 kilometers away from the river. The river mangroves' DNA and their ages also contained clues about when they separated from their coastal relatives.
The team shared its findings in the Proceedings of the National Academy of Sciences on October 12-More than 100,000 years ago, the world was warmer and Sea levels higher. In fact, sea levels reached about 9 meters above today's levels. As a result, land on what is now the Yucatán Peninsula flooded. That allowed coastal mangroves to move inland. When the world cooled again, the mangroves were stuck for from the coast.
“The remarkable resilience of these trees is striking,” says Burelo.“Although they normally live in seawater, they've survived all this time inland. That is incredible.”
This discovery highlights how changes to the past climate have affected the world's coastlines. It also offers a chance to better understand how future sea level rise may affect these ecosystems .
1. What attracted Burelo's attention on the childhood fishing trip?| A．A typical kind of tree. | B．A trap on the coast. |
| C．A fishing net in the river. | D．A team of biologists . |
| A．To predict possible climate changes. | B．To find the substances they are rich in. |
| C．To separate them from their coastal relatives. | D．To get scientific evidence for the tree's origin. |
| A．Where the team carried out their research. |
| B．What once destroyed the Yucatán Peninsula. |
| C．When the sea level became higher than today's. |
| D．How the sea-loving tree ended up far from the coast. |
| A．Growing period. | B．Economic value. |
| C．Adaptive ability. | D．Ecological function. |
【推荐2】Publishers of books for beginning readers are in the business of doing whatever they can to make children develop a love of reading. At times, that means they'll produce books that are more colorful and more packed with pictures. But it turns out that when it comes to learning to read books, more pictures aren't always better.
In fact, simply having more than one picture on a page can negatively(消极地) affect the ability of preschoolers to learn words from that page, according to a new study by researchers at the University of Sussex. “Storybook reading is a great activity to help children increase their vocabularies,” writes co-author Zoe M. Flack in the University's School of Psychology blog.
But the illustrations(插图) can affect how well children will learn new words. “For example,” Flack writes, “We know that children learn words better if illustrations are realistic.” Also, studies have shown that adding bells and whistles(哨声) to storybooks may negatively affect learning, according to Jessica S. Horst, Flack's co-author for the study. “We also know that children look within illustrations for the things they hear in the story, so if the story mentions a girl dropping an ice cream, children will look at the ice cream in the illustration.”
With that in mind, Dr. Horst and Ms. Flack began to wonder what would happen when picture books show many illustrations on a page and how young children who haven't yet learned to read know which illustration to look at while listening to a story. To find out, they read storybooks that displayed either one or two illustrations per page to 36 three-year-old children. As it turns out, children who listened to stories with only one illustration at a time learned twice as many words as children who listened with two or more illustrations.
1. Why do publishers produce books with many colorful pictures?| A．Because such books help kids improve their imagination. |
| B．Because parents are more interested in such books. |
| C．Because they want to help kids love reading. |
| D．Because such books are easier to produce. |
| A．It helps kids learn new words. |
| B．Illustrations aren't that necessary. |
| C．More words should be added to a story. |
| D．It helps kids improve their reading ability. |
| A．Reading is a very important activity. |
| B．One page should have only one illustration for kids. |
| C．Children know what books they should read. |
| D．Children don't really love looking at illustrations. |
| A．choose better stories for children |
| B．produce more types of storybooks |
| C．Produce better books for little kids |
| D．Make more money through producing books |
【推荐3】You can tell a lot about people's general state of mind based on their social media feeds. Are they always tweeting about their biggest annoyances or posting pictures of particularly cute kitties? In a similar fashion, researchers are turning to Twitter for clues about the overall happiness of entire geographic communities.
What they're finding is that regional variation in the use of common phrases produces predictions that don't always reflect the local state of well being. But removing from their analyses just three specific terms — good, love and LOL — greatly improves the accuracy of the methods.
“We're living in a crazy COVID-19 era. And now more than ever, we're using social media to adapt to a new normal and reach out to the friends and family that we can't meet face-to-face.” Kokil Jaidka studies computational linguistics at the National University of Singapore. “But our words aren't useful just to understand what we, as individuals, think and feel. They're also useful clues about the community we live in.”
One of the simpler methods that many scientists use to analyze the data involves correlating words with positive or negative emotions. But when those records are compared with phone surveys that assess regional well-being, Jaidka says, they don't paint an accurate picture of the local zeitgeist.
Being able to get an accurate read on the mood of the population is no laughing matter.
“That's particularly important now, in the time of COVID, where we're expecting a mental health crisis and we're already seeing in survey data the largest decrease in subjective well-being in 10 years at least, if not ever.”
To find out why, Jaidka and her team analyzed billions of tweets from around the United States. And they found that among the most frequently used terms on Twitter are LOL, love and good. And they actually throw the analysis off. Why the disconnect?
“Internet language is really a different beast than regular spoken language. We've adapted words from the English vocabulary to mean different things in different situations.” says Jaidka. “Take, for example, LOL. I've tweeted the word LOL to express irony, annoyance and sometimes just pure surprise. When the methods for measuring LOL as a marker of happiness were created in the 1990s, it still meant laughing out loud.”
"There are plenty of terms that are less misleading," says Jaidka. "Our models tell us that words like excited, fun, great, opportunity, interesting, fantastic and those are better words for measuring subjective well-being."
1. The researchers turn to social media feeds to________.| A．help with the analysis of people's subjective well-being |
| B．locate the most-frequently used words |
| C．prove the disconnect between language and emotions |
| D．make the prediction method more effective |
| A．It didn't reflect the mood of the entire geographic community |
| B．It didn't match the assessment result of the phone surveys. |
| C．It didn't consider the features of Internet language. |
| D．It didn't take the regional variations into account. |
| A．Face-to-face communication is needed to ensure happiness. |
| B．Internet use is to blame for the decrease in subjective well-being. |
| C．Internet language should be abandoned as a source of scientific analysis. |
| D．Less misleading words should be used in assessing subjective well-being. |
【推荐1】Exhibitions in the British Museum
Hokusai: beyond the Great Wave
Katsushika Hokusai (1760-1849) is widely regarded as one of Japan’s most famous and influential artists. He produced works of astonishing quality right up until his death at the age of 90. This new exhibition will lead you on an artistic journey through the last 30 years of Hokusai’s life—a time when he produced some of his most memorable masterpieces.
25 May—13 August 2017
Room 35
Adults￡12, Members/under 16s free
Places of the mind: British watercolour landscapes 1850-1950
Drawn from the British Museum’s rich collection, this is the first exhibition devoted to landscape drawings and watercolours by British artists in the Victorian and modern eras—two halves of very different centuries.
23 February—27 August 2017
Room 90
Free, just drop in
Scythians: warriors of ancient Siberia
This major exhibition explores the story of the Scythians—nomadic tribes and masters of mounted warfare, who flourished between 900 and 200 BC. Their encounters with the Greeks, Assyrians and Persians were written into history but for centuries all trace of their culture was lost—buried beneath the ice.
14 September 2017—14 January 2018
Room 30
Adults￡16.50, Members/under 16s free
Politics and paradise: Indian popular prints from the Moscatelli Gift
This display is part of the Museum’s contribution to the India-UK Year of Culture 2017. It looks at the popular print culture of India from the 1880s until the 1950s.
19 July—3 September 2017
Room 92
Free, just drop in
1. If you are interested in paintings of natural scenery,you will probably go to______.| A．Room 35 | B．Room 90 | C．Room 30 | D．Room 92 |
| A．Hokusai: beyond the Great Wave. |
| B．Scythians: warriors of ancient Siberia. |
| C．Places of the mind: British watercolour landscapes 1850-1950. |
| D．Politics and paradise: Indian popular prints from the Moscatelli Gift. |
| A．In a financial report. | B．In a story book. | C．In a tour guide. | D．In a fashion magazine. |
【推荐2】Since the earliest times, trees have always been very useful and important to men who made use of them in a number of ways for their daily life. Even today trees continue to serve men in so many useful ways.
They supply men with food, fuel (燃料) for burning and building materials in the form of wood. Without trees it would be impossible to build houses, boats and even bridges. Furniture such as tables and chairs is also made of wood.
In the tropics (热带) where it is very warm throughout the year, trees protect men from the terrible heat of the sun. They are also useful in preventing good and fertile (肥沃的) top soil from being washed away during heavy rains which are so common in the tropics. If there were no trees or vegetables of some types to hold back the soil with their roots, heavy rains would wash away the rich surface soil so important for agriculture. The result is that the land becomes useless and unproductive.
There are many desert areas in the world. A long, long time ago these areas must have been rich, fertile areas too, but people in ancient times cut down trees without any plan. They never took the trouble to plant new trees. Strong winds bit by bit blew away the rich surface soil and in the end the land was turned into useless desert where nothing could grow.
1. According to the passage, trees are useful and important because ________.| A．they supply men not only with food, but fuel and building materials |
| B．they protect men from the terrible heat of the sun in the tropics |
| C．they protect the rich surface soil from being washed away |
| D．All the above |
| A．In the tropics, heavy rains are very common. |
| B．Men in the earliest times never made use of trees. |
| C．Trees continue to serve men in many useful ways. |
| D．In the old days, it was impossible to build houses, boats and bridges without trees. |
| A．used to be rich fertile areas | B．are good for plants to grow on |
| C．are formed by cutting down trees with plans | D．are formed by wind blowing |
| A．the rich surface soil is important for agriculture | B．human beings should take care of trees |
| C．human beings have made good use of trees | D．there are many desert areas in the world |
【推荐3】It's been a long, wet winter. Everybody has got colds，and now we are braced for a coronavirus (冠状病毒) pandemic. Improving our immune system has never felt more important，but beyond eating more oranges and hoping for the best. what else can we do?
“When you come into contact with a virus you've never met before,” says Sheena Cruickshank, a professor of immunology at the University of Manchester, “you've got various barriers (屏障) such as skin and microbiome to try to stop it getting into your body.” If a virus breaks these defenses. it has to deal with our white blood cells，or immune cells.
However, our immune systems may have blind spots. “This might mean that our immune response doesn't recognize certain bugs (轻微传染病),” says Cruickshank, “Personally, my immune system is not necessarily very good at seeing colds.” But a healthy lifestyle will ensure your defenses are as good as they can get.
Cruickshank recommends “eating a more varied diet with lots of high-fiber foods”. Being vegetarian isn't a necessity for microbiome health, but the more plant foods you eat, the better.
To be immunologically fit, you need to be physically fit. “White blood cells can be quite inactive.” Says Prof Arne Akbar, the president of the British Society for Immunology, “Exercise activates them by increasing your blood flow，so they can do their surveillance (监督) jobs and seek and destroy in other parts of the body.” The National Health Service says adults should be physically active in some way every day, and do at least 150 minutes a week of moderate aerobic activity (hiking, gardening, cycling) or 75 minutes of vigorous activity (running, swimming fast, and aerobics class).
One of the many happy side-effects of exercise is that it reduces stress, which is next on our list of immune-improving priorities (首要事项). Stress hormones can weaken immune function, a common example of which, says Akbar, is when chickenpox (水痘) strikes twice. If you have had it, the virus never completely goes away. “During periods of stress,” he says, “it can reactivate again and we get ill”.
Exercising and eating well will have the likely knock-on effect of helping you sleep better, which is an extra benefit because a tired body is more likely to get a bug. One study last year found that lack of sleep damaged the disease-fighting ability of a type of lymphocyte called T cells, and research is showing the importance of our natural biorhythms (生物节律) overall. “Your natural biorhythms are, to some extent, controlled by sleep,” says Akbar. “If you've got a regular sleep pattern, you have natural body rhythms and everything's fine. If they go out of order, then you've got problems.”
1. When the barriers fail to prevent a virus entering your body, _______ will come up next.| A．skin | B．blood |
| C．microbiomes | D．immune cells |
| A．She does not lead a healthy life |
| B．Catching a cold is not a terrible thing |
| C．The immune system cannot always be trusted |
| D．Blind spots will not change the immune response |
| A．2 | B．3 |
| C．4 | D．5 |
| A．How to exercise and eat well |
| B．How to enjoy a healthy lifestyle |
| C．How to improve the immune system |
| D．How to get various barriers against coronavirus |
