In 1845, a deadly disease struck the farms of Ireland, killing all the Lumper potato plants. In another place or time, the death of a single crop species might not have been so important. But in Ireland, in 1845, people depended almost on the potato for food. The death of one species caused a terrible famine. Now, some scientists are worried that such a famine could happen again.
Over the centuries, farmers have discovered thousands of different species of food crops. Some can be grown in very hot or cold climates. Others are not affected by certain diseases. However, you won’t find many of these species in your local supermarket. To feed the seven billion people on Earth, most farmers today are growing only species of plants that are easy to produce in large numbers. Meanwhile, thousands of other species are becoming extinct.
For example, in the Philippines, there were once thousands of varieties of rice; now fewer than 100 are grown there. Experts believe that over the past century, we have allowed more than half of the world’s food varieties to disappear.
One solution to this problem is to collect and store the seeds (种子) of as many different plant varieties as we can before they disappear. The idea was first suggested by Russian scientist Nikolay Vavilov. In the 1920s and 30s, he collected around 400,000 seeds. More recently, others are continuing the work he began.
In the U.S. state of Iowa, Diane Ott Whealy wanted to protect historic plant varieties. She started a place called Heritage Farm, where people can store and trade seeds.
More importantly, the people at Heritage Farm don’t just store the seeds; they plant them. By doing this, they are reintroducing foods into the marketplace that haven’t been grown for years. These food species are not just special in flavor. They also offer farmers food solutions for the future, from the past.
1. What caused many people to die in Ireland in 1845?| A．Food pollution. |
| B．Poisonous potatoes. |
| C．An incurable disease. |
| D．Lack of enough food. |
| A．Species of food crops. | B．Potato plants. | C．Farmers. | D．Seeds. |
| A．To show many food species have disappeared. |
| B．To explain how to increase food production. |
| C．To stress the importance of food diversity. |
| D．To prove the necessity of growing rice. |
| A．It’s dangerous to grow new food species. |
| B．The work started by Nikolay Vavilov was useless. |
| C．Storing seeds and planting them are both important. |
| D．Foods grown from older seeds are cheaper but taste bad. |
相似题推荐
【推荐1】How to Build a Natural Swimming Pool
Whether you like to practice your dolphin dives or idle away the day on a raft, swimming is one of summer’s perfect pleasures. With a minimum of materials, you can create a cooling summer retreat in your backyard.
Though common in Europe, natural swimming pools, are in their early stage in the United States. You can ask most American swimming-pool contractors (承包商) to build a backyard pool.
But in recent years, a few builders and a growing number of homeowners have learned how to build pools.
Natural swimming pools require no harmful chemicals, are fairly low-tech.
| A．The plants enrich the pool with oxygen. |
| B．Chances are that they will roll out a long list of goods. |
| C．You can make your pool as shallow or as deep as you want. |
| D．And once established, they call for only a bit of management. |
| E．It is the most ecological and economic way to build a conventional pool. |
| F．They don’t rely on a mass of manufactured materials and chemical additives. |
| G．The result is an ecological system that is relatively inexpensive to construct. |
【推荐2】Building Trust in a Relationship Again
Trust is a learned behavior that we gain from past experiences.
Unfortunately, we’ve all been victims of betrayal. Whether we’ve been stolen from, lied to, misled, or cheated on, there are different levels of losing trust. Sometimes people simply can’t trust anymore.
●Learn to really trust yourself. Having confidence in yourself will help you make better choices because you can see what the best outcome would be for your well-being.
●
● You didn’t lose "everything". Once trust is lost, what is left? Instead of looking at the situation from this hopeless angle, look at everything you still have and be thankful for all of the good in your life.
| A．It is putting confidence in someone. |
| B．Believe in yourself. |
| C．Here are some tips for you. |
| D．Stop regarding yourself as the victim. |
| E．They’ve been too badly hurt and they can’t bear to let it happen again. |
| F．Seeing the positive side of things doesn’t mean you’re ignoring what happened |
| G．This knowledge carries over in their attitude toward their future relationships. |
【推荐3】Recent research indicates that the ability to remain calm under pressure has a direct link with work performance. Talent Smart has conducted research on over a million people and found that 90% of top performers are skilled at managing their emotions in times of stress.
Research conducted at the University of California found that people who focused daily on feeling grateful for what they’d experienced improved moods, energy, and physical health.
Taking regular time off to relax can help keep stress under control. Technology enables constant communication and the expectation that you should be available all the time.
The easiest way to make stress off-and-off lies in something that people do every day: breathing. The practice of focusing on breathing teaches the brain to let go of stressful thoughts for a while. Close the door and just sit in a chair and breathe.
| A．We should learn to take control |
| B．Sleep shortage raises stress levels |
| C．In addition, positive thoughts help reduce stress |
| D．However, this exposes people to stress more frequently |
| E．The goal is to spend the entire time focusing only on breathing |
| F．In the following section four effective ways to manage stress will be outlined |
| G．A big step in managing stress involves controlling your reactions to situations |
【推荐1】Science Advances published a new research report, saying bees are capable of addition and subtraction (减法)in Arithmetic(算术) learning—using colors in the place of plus and minus symbols.
It isn’t unusual to see the ability to count—or at least distinguish between differing quantities in the animal kingdom—Such ability has been seen in frogs, spiders, and even fish. But solving equations (方程式) using symbols is rare, so far only achieved by famously brainy animals such as chimpanzees. The previous research says the social insects, ants, can count to four and understand the concept of zero and researchers wanted to test the limits of what their tiny brains can do.
The experiment goes like this. Scientists trained 14 bees to link the colors blue and yellow to addition and subtraction, respectively. They put the bees at the entrance of a Y-shaped maze (迷 宫), where they were shown several shapes in either yellow or blue. If the shapes were blue, bees got a reward if they went to the end of the maze with one more blue shape (the other end had one less blue shape); if the shapes were yellow, they got a reward if they went to the end of the maze with one less yellow shape.
The testing worked the same way: Bees that “subtracted” one shape when they saw yellow, or “added” one shape when they saw blue were considered to have aced the test. The bees got the right answer 63% to 72% of the time, depending on the type of equation and the direction of the right answer—much better than random guesses would allow.
While the results came from just 14 bees, researchers say the advance is exciting. If a brain about 20,000 times smaller than ours can perform maths using symbols, it could pave the way to novel methods in artificial intelligence (AI) and machine learning. Just don’t ask the bees to do your homework anytime soon.
1. From the first two paragraphs, we know that the scientists conduct the research______.| A．to get access to machine learning |
| B．to explain the meaning of colors |
| C．to test the power of tiny brains |
| D．to teach bees to learn maths |
| A．given up | B．got through |
| C．entered for | D．checked over |
| A．Development of AI. | B．Arithmetic learning. |
| C．Protection of animals. | D．Language acquisition. |
| A．Bees “Like” Counting |
| B．Bees “Tell” Colors Apart |
| C．Bees “Perform” Maths Using Shapes |
| D．Bees “Get” Addition and Subtraction |
【推荐2】Crown shyness (树冠羞避) is a mysterious natural phenomenon in which the crowns of some tree species do not touch each other, but get separated by a gap clearly seen from ground level. The effect usually occurs between trees of the same species, but has also been observed between trees of different species.
There are many theories going around, most of which make sense, but no one has been able to prove without the shadow of a doubt why some trees avoid touching each other.
In his 1955 book Growth Habits of the Eucalypts, Australian forester M. R. Jacobs writes that the growing tips of the trees are sensitive to abrasion (擦伤)，which results in crown shyness phenomenon. This theory was also supported by Dr. Miguel Franco. Some experiments have shown that if trees displaying crown shyness are artificially prevented from swaying (摇摆)in the wind and touching each other, they gradually fill up the gaps between them.
But while the above theory is arguably the most widespread, it's certainly not the only one. Some scientists have suggested that crown shyness is a mechanism to stop the spreading of leaf-eating insects. The gaps mean pests wouldn't be able to reach other trees, so they are the tree's natural defense method.
One Malaysian scholar studied many trees, but found no traces of abrasions, despite their clear crown shyness. Instead, he suggests that the growing tips of the trees were sensitive to light levels and stopped growing when they got too close to other trees. Plants are able to sense how close they are to other plants and in order to get more light, they give off some chemical to stop other trees from growing too close.
Whatever the reason, one thing is for sure, plants are more intelligent than people.
1. What can we know about crown shyness?| A．It can cause abrasion between trees. |
| B．It only happens between the same species. |
| C．It has been discovered for only half a century. |
| D．No agreement has been reached about its real cause. |
| A．The trees will stop growing and even die. |
| B．The gaps between the trees will grow wider. |
| C．The crown shyness phenomenon will disappear. |
| D．The gaps between the trees will remain the same. |
| A．Tip. | B．Way. |
| C．Theory. | D．Plan. |
| A．Trees have special ways to attack others. |
| B．Some insects stop trees growing too close. |
| C．Trees compete with their neighbors for light. |
| D．Trees won't touch each other to avoid diseases. |
【推荐3】Fire ants dig tunnels efficiently by only a small percentage of the group doing most of the work. Free-loaders just sit around while their hard-working colleagues get things done. But might freeloaders actually be necessary for society to function efficiently? The answer could be yes.
Fire ants are highly social organisms. So, Goldman, a physicist at Georgia Tech, and his colleagues wanted to know how individual ants knew what to do without a central leader issuing orders. To find out, Goldman's team labeled individual fire ants with paint and then watched them dig their narrow tunnels —barely wide enough for two workers. Turns out, just 30 percent of the ants did 70 percent of the labor. “I was surprised that we ended up with so few workers actually doing the work at any one time. ” A quarter of the ants never even entered the tunnel. Others crawled inside, but left without digging single grain of dirt. These idling behaviors ensured the tunnels did not get clogged with insect traffic, which would make the construction process stop.
And when the scientists removed the five hardest working ants from the colony, others immediately jumped in to compensate (补偿) — with no reduction in the group's productivity. It seems that it doesn’t matter which ants are working or freeloading at a given time, as long as there is some division of labor to keep the tunnels flowing smoothly. The findings are in the journal Science.
The study could have implications for robotics. Imagine groups of robots sent to search rubble (碎石) for disaster survivors. Or nanobots (纳米机器人) coursing through our bodies to diagnose illness and deliver targeted medical treatment. Such robot groups will need to avoid getting jammed up in tight spaces. It might be necessary to program them so some just sit back and watch their comrades work.
1. How do fire ants get the work done when digging tunnels?| A．Only the leaders do most of the work. |
| B．They all work under the order of one leader. |
| C．They all cooperate together to do the work efficiently. |
| D．Individual fire ants know their tasks and work efficiently. |
| A．crowded | B．transported |
| C．organized | D．covered |
| A．The ants will have no idea what to do. |
| B．Other ants will take their place and do the work. |
| C．The tunnels will get blocked and the work will stop. |
| D．The leader will compensate them and give them food as the reward. |
| A．fire ants are the most diligent insects. |
| B．scientists may diagnose illness more easily. |
| C．people may feel happy when they watch their colleagues do nothing. |
| D．scientists can deal with robotics better when coming to specific programs. |
【推荐1】Junk food is everywhere. We’re eating way too much of it. Most of us know what we’re doing and yet we do it anyway.
So here’s a suggestion offered by two researchers at the Rand Corporation: Why not take a lesson from alcohol control policies and apply them to where food is sold and how it’s displayed?
“Many policy measures to control obesity (肥胖症) assume that people consciously and rationally choose what and how much they eat and therefore focus on providing information and more access to healthier foods,” note the two researchers.
“In contrast,” the researchers continue, “many regulations that don’t assume people make rational choices have been successfully applied to control alcohol, a substance - like food - of which immoderate (过度的) consumption leads to serious health problems.”
The research references studies of people’s behavior with food and alcohol and results of alcohol restrictions, and then lists five regulations that the researchers think might be promising if applied to junk foods. Among them:
Density restrictions: licenses to sell alcohol aren’t handed out unplanned to all comers but are allotted (分配) based on the number of places in an area that already sell alcohol. These make alcohol less easy to get and reduce the number of psychological cues to drink.
Similarly, the researchers say, being presented with junk food stimulates our desire to eat it. So why not limit the density of food outlets, particularly ones that sell food rich in empty calories? And why not limit sale of food in places that aren’t primarily food stores?
Display and sales restrictions: California has a rule prohibiting alcohol displays near the cash registers in gas stations, and in most places you can’t buy alcohol at drive-through facilities. At supermarkets, food companies pay to have their wares in places where they’re easily seen. One could remove junk food to the back of the store and ban them from the shelves at checkout lines. The other measures include restricting portion sizes, taxing and prohibiting special price deals for junk foods, and placing warning labels on the products.
1. What does the author say about junk food?| A．People should be educated not to eat too much. |
| B．It is widely consumed despite strict policies. |
| C．Its temptation is too strong for people to resist. |
| D．It causes more harm than is generally realized. |
| A．Guiding people to make rational choices about food. |
| B．Enhancing people’s awareness of their own health. |
| C．Borrowing ideas from alcohol control measures. |
| D．Resorting to economic, legal and psychological means. |
| A．They are based on wrong assumptions. |
| B．They provide misleading information. |
| C．They should be implemented effectively. |
| D．They help people make rational choices. |
| A．Few people are able to resist alcohol’s temptations. |
| B．There are already too many stores selling alcohol. |
| C．Drinking strong alcohol can cause social problems. |
| D．Easy access leads to customer’ over-consumption. |
【推荐2】The Chinese philosopher (哲学家) Confucius once said, “Time flows away like the water in the river.” This is especially true as the novel coronavirus pneumonia outbreak has affected millions of people in China, and the whole nation has been working day and night to fight the epidemic.
In late January, when an increasing number of people in Wuhan were suspected to be infected, and hospitals didn't have adequate beds for them, two special hospitals—Lei shenshan Hospital and Huo shenshan Hospital were built. These two makeshift (临时的) hospitals were built to treat pneumonia patients infected with the novel coronavirus. Huo shenshan Hospital has 1,000 beds and covers 33,900 square meters, and Lei shenshan Hospital has 1,500 beds and a total area of about 79,000 square meters. More than 4,000 workers worked 24/7 in two shifts, and nearly 1,000 large-scale pieces of equipment and transport vehicles helped the project on site. The two hospitals were built in an amazingly short time. It only took 10 days for people to build Huo shenshan, and 14 days for Lei shenshan.
This certainly wowed many people overseas. “It's incredible that two hospitals with 2,500 beds can be built in a short period. It's just hard to believe,” a foreigner named Stuart told People's Daily. In the meantime, Chinese companies have also taken actions quickly in this battle.
“The automobile industry is highly industrialized with strong capabilities in comprehensive manufacturing, purchasing materials, production lines and output of technologies,” Shi Jianhua, deputy secretary-general of China Association of Automobile Manufacturers, told CCTV News. “In this special time, when the nation needs more masks, it's time for us to quickly respond and shoulder the social responsibilities.”
Indeed, a fast response is crucial in any crisis. In this special time, China can't afford to waste a second in the fight against the epidemic. After all, time equals life during this crisis.
1. Confucius' saying “Time flows away like the water in the river.” is mentioned to ______.| A．arouse readers' interest in the passage. | B．introduce the subject of the passage. |
| C．present the background information. | D．stress the value of time in epidemic. |
| A．They are new hospitals for health care in Wuhan. |
| B．They were built in minimal time. |
| C．Over 4,000 workers worked continuously. |
| D．Stuart found them too massive to believe. |
| A．had no medical supplies factories before. |
| B．guarantees whoever in need enough masks. |
| C．has capabilities to give timely response. |
| D．has strong abilities in manufacturing. |
| A．China fights epidemic against the clock. |
| B．Two special hospitals were constructed. |
| C．Chinese firms acted quickly and effectively. |
| D．Time is crucial for people in overcoming crisis. |
【推荐3】Antarctica has actually become a kind of space station — a unique observation post for detecting important changes in the world’s environment. Remote from major sources of pollution and the complex geological and ecological systems that are common elsewhere, Antarctica makes possible scientific measurements that are often sharper and easier to interpret than those made in other parts of the world.
Therefore, growing numbers of scientists see Antarctica as a distant-early-warning sensor, where potentially dangerous global trends may be spotted before they show up to the north. One promising field of investigation is glaciology. Scholars from the United States, Switzerland, and France are pursuing seven separate but related projects that reflect their concern for the health of the West Antarctic Ice Sheet — a concern they believe the whole world should share.
The Transantarctic Mountain, some of them more than 14,000 feet high, divide the continent into two very different regions. The part of the continent to the “east” of the mountains is a high plateau (高原) covered by an ice sheet nearly two miles thick. “West” of the mountain, the half of the continent south of the Americas is also covered by an ice sheet, but there the ice rests on rock that is mostly well below sea level. If the West Antarctic Ice Sheet disappeared, the western part of the continent would be reduced to a few and far gathering of island.
While ice and snow are obviously central to many environmental experiments, others focus on the mysterious “dry valley” of Antarctica. The valleys contain little ice or snow even in the depths of winter. Through the mountains of southern Victoria Land, these valleys once held enormous glaciers that extended 9,000 feet downside to the Ross Sea. Now the glaciers are gone, perhaps due to the global warming trend during the 10,000 years since the ice age. Even the snow that falls in the dry valleys is blown away by strong winds that roars down from the polar plateau to the sea.
Despite the mysterious aspect of the dry valleys, some scientists believe they may carry the hope of the environment. Some scientists believe that in some cases the dry valleys may absorb pollutants faster than pollutants enter them.
1. What is the best title for this passage?| A．Antarctica and environmental Problems. |
| B．Antarctica: a high plateau. |
| C．Antarctica: a Unique Observation Post. |
| D．Antarctica: a Mysterious Place. |
| A．The western part of the continent would be disappeared. |
| B．The western part of the continent would be reduced. |
| C．The western part of the continent would become a fragmentary island. |
| D．The western part of the continent would be reduced to a gathering of island. |
| A．Strong wind blows the snow away. |
| B．It rarely snows. |
| C．Because of the global warming trend and fierce wind. |
| D．Ice sheets. |
| A．The “Dry Valleys” have nothing left inside. |
| B．The “Dry Valleys” never held glaciers. |
| C．The “Dry Valleys” may carry a message of hope. |
| D．The “Dry Valleys” are useless to scientists. |
【推荐1】Back in freshman year，I found myself wondering whether it should really be called “volunteering” if students only do it because they have to.
I ended up volunteering at Weyrich Health Center，helping elderly patients with daily tasks. The more I did these tasks，the more disconnected I felt from the seniors. Though I felt bad for them，I did not want to interact with them.
Then one rainy day，I met Colonel Hemsworth. He invited me to his table and asked for some company. I regarded this as another boring task. However，when I listened to his stories，I learned that he was a brilliant war veteran(老兵)，and I found his tales interesting.
After my brief talk with the Colonel，I realized that I shared common characters with all the seniors. I_felt_like_an_oxygen_molecule(分子)－ready_to_form_a_relationship－rather_than_an_isolated_gas.
I met with many learned senior citizens who shared their experiences and wisdom. No longer did I walk aimlessly down the hallways. I found myself enjoying talking with these people as I learned their histories. Why hadn't I realized sooner that volunteer work could enlighten me?
Some people argue that volunteering and working for change does not help. However，they fail to realize that the world is constantly changing and humans must adapt. My experience at Weyrich Health Center has taught me that refusing to change one's views and accept new ones leads to short－term goals that finally disappear. Communication with others is an important part of life. Volunteering is not just a requirement or a way to improve your resume，it is a time for service and personal growth.
Now I enjoy volunteering my time surrounded by seniors who bring history alive for me. By communicating with them，I have developed into a more dynamic person.
1. What's the author's initial attitude towards volunteering?| A．Positive. | B．Satisfied. |
| C．Doubtful. | D．Unwilling. |
| A．He liked the author very much. |
| B．He wanted the author to accompany him. |
| C．He wanted to work with the author. |
| D．He planned to teach the author something. |
| A．The author had desire to communicate with the seniors. |
| B．the author wanted to do a chemical experiment with gas. |
| C．The author imagined himself to be part of isolated gas. |
| D．The author would like to be an oxygen molecule. |
| A．Other people's attitude towards volunteering. |
| B．The importance of communicating with others. |
| C．The important meaning of humans adapting to changes. |
| D．The lessons the author has learned from volunteering. |
【推荐2】Can small, organic agriculture really feed the world? Won't we need science to produce enough food as the world population is growing to 9 billion by 2050? The answer to both questions is YES—but that science may look different than you think.
We've been told that the only way we'll be able to feed the growing population is through the science of GM crops and chemicals. But the latest scientific studies are saying just the opposite. In study after study, the message about agriculture is: To feed the world, we need to support sustainable（可持续的）agriculture on different local family farms that work with nature.
In 2008, an international study found that sustainable agriculture, not GM crops, shows more hope of ending hunger. The International Assessment of Agricultural Knowledge. Science, and Technology for Development（known as the IAASTD）, calls for a change of the world's food and farming systems.
The IAASTD reports that industrial agriculture has greatly destroyed the world's soils and other natural resources, and now is causing water pollution, energy crisis, and air pollution. The report warns that expensive, short-term ways—including GM crops are not likely to cut down long-term hunger, and could even make environment and social problems worse in many places.
A recent report by the UN Environment Program shows that food problems are becoming more serious and strongly supports sustainable agriculture on small family farms. It also shows that a worldwide change to organics can actually increase the world's food production by as much as 50%—enough to feed a population of 9 billion people with the land we have now. GM crops, once popular, are now being questioned worldwide.
1. What is the best way to feed the growing population of the world?| A．In expensive, short-term ways. |
| B．By encouraging industrial agriculture. |
| C．By developing small, organic agriculture. |
| D．Through the science of GM crops and chemicals. |
| A．The science of GM crops. |
| B．Working on small family farms. |
| C．A fast way to increase the world's food production. |
| D．An approach to agriculture without harming the environment. |
| A．There will be less food problems if we use big family farms. |
| B．There will be less food problems if the world supports GM food. |
| C．There will be less food problems if we increase a lot of farm land. |
| D．There will be less food problems if the world supports sustainable agriculture. |
| A．The causes of food problems. |
| B．The disadvantages of GM crops. |
| C．The development of industrial agriculture. |
| D．The disadvantages of sustainable agriculture. |
【推荐3】Transport has a lot to answer for when it comes to harming the planet. While cars and trains are moving towards greener, electric power, emissions from air travel are expected to increase massively by 2050. If we want big green sky solutions, we need blue sky thinking Fortunately, there's plenty of that happening right now, particularly the short-haul flights powered by batteries.
Harbour Air is the largest seaplane airline in North America, flying 30, 000 commercial flights in 40 seaplanes each year. Significantly, all Harbour Air routes last less than 30 minutes, making it perfectly fit for electric engines. “As an airline, we're currently in the process of turning all our planes into electric airplanes. says CEO Greg Mc Dougall. To make this happen, the airline has partnered up with MagniX to create the worlds first commercial flight with an electric engine.
Making the skies electric isn't just good for the environment, it also makes sound financial sense: a small aircraft uses $400 on conventional fuel for a 100-mile flight, while an electric one costs $8-12 for the same distance, and that's before you factor in the higher maintenance costs of a traditional engine. There's also the added bonus that electric planes are just much more pleasant to fly in. No loud engine noise, no smell of fuel, just environmentally friendly peace and quiet.
While there has been real progress in the e-plane industry, the technical challenges that remain are keeping everyone's feet firmly on the ground. A battery, even a lithium one, only provides 250 watt-hours per kilogram; compare this to liquid fuel, which has a specific energy of 11, 890 watt-hours per kilogram. Carrying adequate batteries, however, would make the plane too heavy to get off the ground. In aircraft, where every bit of weight counts, this can't just be ignored.
The transition （过渡） from gas to electric in the automobile industry has been made easier by hybrids-vehicles powered by both fuel and electricity. Many believe the same pattern could be followed in the air. Fuel consumption could be reduced as the electric component is switched on at key parts of the journey, especially on take-off and landing.
It's certainly an exciting time for electric flying. With companies like Harbour Air taking the lead, battery-powered planes, especially on short-haul journeys, are set to become a reality in the next few years.
1. According to Para. l, what is happening in air transport?| A．New explorations of the sky are being launched. |
| B．Pollution caused by batteries is being controlled. |
| C．Efforts are being made to make air travel greener. |
| D．Demand for short-haul flights is increasing massively. |
| A．It runs short route |
| B．It has a strong partner. |
| C．Its planes can land on the sea. |
| D．It has planes with powerful engines. |
| A．give passengers more pleasant views |
| B．bring airlines more financial benefits |
| C．offer more enjoyable flying experiences |
| D．cost less in maintenance than traditional ones |
| A．To improve the ground service for e-planes. |
| B．To find qualified technicians for e-plane industry. |
| C．To calculate the energy needed to power e-planes. |
| D．To balance power and weight of batteries in e-planes. |
| A．To produce new electric components. |
| B．To increase battery consumption. |
| C．To use mixed-power technology. |
| D．To expand the landing field. |
| A．Short-sighted. |
| B．Wait-and-see. |
| C．Optimistic. |
| D．Skeptical. |
