1 . According to a recent study in the Journal of Consumer Research, both the size and consumption habits of our eating companions can influence our food intake. And contrary to existing research that says you should avoid eating with heavier people who order large portions(份), it's the beanpoles with big appetites you really need to avoid.
To test the effect of social influence on eating habits, the researchers conducted two experiments. In the first, 95 undergraduate women were individually invited into a lab to ostensibly(表面上)participate in a study about movie viewership. Before the film began, each woman was asked to help herself to a snack. An actor hired by the researchers grabbed her food first. In her natural state, the actor weighed 105 pounds. But in half the cases she wore a specially designed fat suit which increased her weight to 180 pounds.
Both the fat and thin versions of the actor took a large amount of food. The participants followed suit, taking more food than they normally would have. However, they took significantly more when the actor was thin.
For the second test, in one case the thin actor took two pieces of candy from the snack bowls. In the other case, she took 30 pieces. The results were similar to the first test: the participants followed suit but took significantly more candy when the thin actor took 30 pieces.
The tests show that the social environment is extremely influential when we're making decisions. If this fellow participant is going to eat more, so will I. Call it the “I’ll have what she's having” effect. However, we'll adjust the influence. If an overweight person is having a large portion, I'll hold back a bit because I see the results of his eating habits. But if a thin person eats a lot, I'll follow suit. If he can eat much and keep slim, why can't I?
1. What is the recent study mainly about?| A．Food safety. | B．Movie viewership. |
| C．Consumer demand. | D．Eating behavior. |
| A．Big eaters. | B．Overweight persons. |
| C．Picky eaters. | D．Tall thin persons. |
| A．To see how she would affect the participants. |
| B．To test if the participants could recognize her. |
| C．To find out what she would do in the two tests. |
| D．To study why she could keep her weight down. |
| A．How hungry we are. | B．How slim we want to be. |
| C．How we perceive others. | D．How we feel about the food. |
2 . When you were trying to figure out what to buy for the environmentalist on your holiday list, fur probably didn’t cross your mind. But some ecologists and fashion (时装)enthusiasts are trying to bring back the market for fur made from nutria(海狸鼠).
Unusual fashion shows in New Orleans and Brooklyn have showcased nutria fur made into clothes in different styles. “It sounds crazy to talk about guilt-free fur-unless you understand that the nutria are destroying vast wetlands every year”, says Cree McCree, project director of Righteous Fur.
Scientists in Louisiana were so concerned that they decided to pay hunters $5 a tail. Some of the fur ends up in the fashion shows like the one in Brooklyn last month.
Nutria were brought there from Argentina by fur farmers and let go into the wild. “The ecosystem down there can’t handle this non-native species(物种).It’s destroying the environment. It’s them or us.” says Michael Massimi, an expert in this field.
The fur trade kept nutria in check for decades，but when the market for nutria collapsed in the late 1980s，the cat-sized animals multiplied like crazy.
Biologist Edmond Mouton runs the nutria control program for Louisiana. He says it’s not easy to convince people that nutria fur is green, but he has no doubt about it. Hunters bring in more than 300,000 nutria tails a year, so part of Mouton’s job these days is trying to promote fur.
Then there’s Righteous Fur and its unusual fashion. Model Paige Morgan says，”To give people a guilt-free option that they can wear without someone throwing paint on them-I think that’s going to be a massive thing, at least here in New York.” Designer Jennifer Anderson admits it took her a while to come around to the opinion that using nutria fur for her creations is morally acceptable. She is trying to come up with a label to attach to nutria fashions to show it is eco-friendly.
1. What is the purpose of the fashion shows in New Orleans and Brooklyn?| A．To promote guilt-free fur. |
| B．To expand the fashion market. |
| C．To introduce a new brand. |
| D．To celebrate a winter holiday. |
| A．Nutria damage the ecosystem seriously. |
| B．Nutria are an endangered species. |
| C．Nutria hurt local cat-sized animals. |
| D．Nutria are illegally hunted. |
| A．Boomed. | B．Became mature. | C．Remained stable. | D．Crashed. |
| A．It’s formal. | B．It’s risky. | C．It’s harmful. | D．It’s traditional. |
3 . For those who can stomach it, working out before breakfast may be more beneficial for health than eating first, according to a study of meal timing and physical activity.
Athletes and scientists have long known that meal timing affects performance. However, far less has been known about how meal timing and exercise might affect general health.
To find out, British scientists conducted a study. They first found 10 overweight and inactive but otherwise healthy young men, whose lifestyles are, for better and worse, representative of those of most of us. They tested the men’s fitness and resting metabolic (新陈代谢的) rates and took samples (样品) of their blood and fat tissue.
Then, on two separate morning visits to the scientists’ lab, each man walked for an hour at an average speed that, in theory, should allow his body to rely mainly on fat for fuel. Before one of these workouts, the men skipped breakfast, meaning that they exercised on a completely empty stomach after a long overnight fast (禁食). On the other occasion, they ate a rich morning meal about two hours before they started walking.
Just before and an hour after each workout, the scientists took additional samples of the men’s blood and fat tissue.
Then they compared the samples. There were considerable differences. Most obviously, the men displayed lower blood sugar levels at the start of their workouts when they had skipped breakfast than when they had eaten. As a result, they burned more fat during walks on an empty stomach than when they had eaten first. On the other hand, they burned slightly more calories (卡路里), on average, during the workout after breakfast than after fasting.
But it was the effects deep within the fat cells that may have been the most significant, the researchers found. Multiple genes behaved differently, depending on whether someone had eaten or not before walking. Many of these genes produce proteins (蛋白质) that can improve blood sugar regulation and insulin (胰岛素) levels throughout the body and so are associated with improved metabolic health. These genes were much more active when the men had fasted before exercise than when they had breakfasted.
The implication of these results is that to gain the greatest health benefits from exercise, it may be wise to skip eating first.
1. The underlined expression “stomach it” in Paragraph 1 most probably means “______”.| A．digest the meal easily | B．manage without breakfast |
| C．decide wisely what to eat | D．eat whatever is offered |
| A．Their lifestyles were typical of ordinary people. |
| B．Their lack of exercise led to overweight. |
| C．They could walk at an average speed. |
| D．They had slow metabolic rates. |
| A．They successfully lost weight. | B．They consumed a bit more calories. |
| C．They burned more fat on average. | D．They displayed higher insulin levels. |
| A．A workout after breakfast improves gene performances. |
| B．Too much workout often slows metabolic rates. |
| C．Lifestyle is not as important as morning exercise. |
| D．Physical exercise before breakfast is better for health. |
4 . Albert Einstein’s 1915 masterpiece “The Foundation of the General Theory of Relativity” is the first and still the best introduction to the subject, and I recommend it as such to students. But it probably wouldn’t be publishable in a scientific journal today.
Why not? After all, it would pass with flying colours the tests of correctness and significance. And while popular belief holds that the paper was incomprehensible to its first readers, in fact many papers in theoretical physics are much more difficult.
As the physicist Richard Feynman wrote, “There was a time when the newspapers said that only 12 men understood the theory of relativity. I do believe there might have been a time when only one man did, because he was the only guy who caught on, before he wrote his paper. But after people read the paper a lot understood the theory of relativity in some way or other, certainly more than 12.”
No, the problem is its style. It starts with a leisurely philosophical discussion of space and time and then continues with an exposition of known mathematics. Those two sections, which would be considered extraneous today, take up half the paper. Worse, there are zero citations of previous scientists’ work, nor are there any graphics. Those features might make a paper not even get past the first editors.
A similar process of professionalization has transformed other parts of the scientific landscape. Requests for research time at major observatories or national laboratories are more rigidly structured. And anything involving work with human subjects, or putting instruments in space, involves piles of paperwork.
We see it also in the Regeneron Science Talent Search, the Nobel Prize of high school science competitions. In the early decades of its 78-year history, the winning projects were usually the sort of clever but naive, amateurish efforts one might expect of talented beginners working on their own. Today, polished work coming out of internships(实习) at established laboratories is the norm.
These professionalizing tendencies are a natural consequence of the explosive growth of modern science. Standardization and system make it easier to manage the rapid flow of papers, applications and people. But there are serious downsides. A lot of unproductive effort goes into jumping through bureaucratic hoops(繁文缛节), and outsiders face entry barriers at every turn.
Of course, Einstein would have found his way to meeting modern standards and publishing his results. Its scientific core wouldn’t have changed, but the paper might not be the same taste to read.
1. According to Richard Feynman, Einstein’s 1915 paper ________.| A．was a classic in theoretical physics |
| B．turned out to be comprehensible |
| C．needed further improvement |
| D．attracted few professionals |
| A．Unrealistic. | B．Irrelevant. |
| C．Unattractive. | D．Imprecise. |
| A．The application of research findings. |
| B．The principle of scientific research. |
| C．The selection of young talents. |
| D．The evaluation of laboratories. |
| A．What makes Einstein great? |
| B．Will science be professionalized? |
| C．Could Einstein get published today? |
| D．How will modern science make advances? |
5 . Great work is work that makes a difference in people’s lives, writes David Sturt, Executive Vice President of the O.C. Tanner Institute, in his book Great Work: How to Make a Difference People Love. Sturt insists, however, that great work is not just for surgeons or special-needs educators or the founders of organizations trying to eliminate poverty in sub-Saharan Africa. The central theme of Great Work, according to Sturt, is that anyone can make a difference in any job. It’s not the nature of the job, but what you do with the job that counts. As proof, Sturt tells the story of a remarkable hospital cleaner named Moses.
In a building filled with doctors and nurses doing great life-saving work, Moses the cleaner makes a difference. Whenever he enters a room, especially a room with a sick child, he engages both patients and parents with his optimism and calm, introducing himself to the child and, Sturt writes, speaking “little comments about light and sunshine and making things clean.” He comments on any progress he sees day by day (“you’re sitting up today, that’s good.”) Moses is no doctor and doesn’t pretend to be, but he has witnessed hundreds of sick children recovering from painful surgery, and parents take comfort from his encouraging words. For Matt and Mindi, whose son McKay was born with only half of a heart, Moses became a close friend. As Sturt explains, “Moses took his innate (与生俱来的) talents (his sensitivity) and his practical wisdom (from years of hospital experience) and combined them into a powerful form of patient and family support that changed the critical-care experience for Mindi, Matt and little McKay.”
How do people like Moses do great work when so many people just work? That was the central question raised by Sturt and his team at the O.C. Tanner Institute, a consulting company specialized in employee recognition and rewards system.
O.C. Tanner launched an exhaustive Great Work study that included surveys to 200 senior executives, a further set of surveys to 1,000 managers and employees working on projects, an in-depth qualitative study of 1.7 million accounts of award-winning work (in the form of nominations (提名) for awards from corporations around the world), and one-on-one interviews with 200 difference makers. The results of the study revealed that those who do great work refuse to be defeated by the constraints of their jobs and are especially able to reframe their jobs: they don’t view their jobs as a list of tasks and responsibilities but see their jobs as opportunities to make a difference. No matter, as Moses so ably exemplifies (例证), what that job may be.
1. According to Sturt, which of the following is TRUE?| A．It’s not the nature of the job, but what you do that makes a difference. |
| B．Anyone in the world is responsible to delete poverty and change the world. |
| C．Anyone can make a difference in people’s lives no matter what kind of job he does. |
| D．Surgeons, special-needs educators and founders of organizations can succeed more easily. |
| A．By keeping optimistic and calm when facing patients and their parents at hospital. |
| B．By showing his special gift and working experience when working at hospital. |
| C．By showing his sympathy and kindness to patients when entering their rooms. |
| D．By pretending to be a doctor or nurse when entering a room with a sick child. |
| A．demands | B．advantages | C．disadvantages | D．limitations |
| A．Great work is work that makes a difference in people’s lives no matter what you do. |
| B．If a boss has trouble recognizing his employees, he can ask O. C. Tanner for advice. |
| C．Moses makes a difference through his sensitivity and his practical wisdom. |
| D．Those who do great work are never defeated by others or their jobs themselves. |
6 . Elizabeth Spelke, a cognitive (认知的) psychologist at Harvard, has spent her career testing the world's most complex learning system-the mind of a baby. Babies might seem like no match for artificial intelligence (AI). They are terrible at labeling images, hopeless at mining text, and awful at video games. Then again, babies can do things beyond the reach of any AI. By just a few months old, they’ve begun to grasp the foundations of language, such as grammar. They’ve started to understand how to adapt to unfamiliar situations.
Yet even experts like Spelke don’t understand precisely how babies — or adults, for that matter — learn. That gap points to a puzzle at the heart of modern artificial intelligence: We're not sure what to aim for.
Consider one of the most impressive examples of AI, Alpha Zero, a programme that plays board games with superhuman skill. After playing thousands of games against itself at a super speed, and learning from winning positions, Alpha Zero independently discovered several famous chess strategies and even invented new ones. It certainly seems like a machine eclipsing human cognitive abilities. But Alpha Zero needs to play millions more games than a person during practice to learn a game. Most importantly, it cannot take what it has learned from the game and apply it to another area.
To some AI experts, that calls for a new approach. In a November research paper, Francois Chollet, a well-known AI engineer, argued that it’s misguided to measure machine intelligence just according to its skills at specific tasks. “Humans don’t start out with skills; they start out with a broad ability to acquire new skills,” he says. “What a strong human chess player is demonstrating is not only the ability to play chess, but the potential to fulfill any task of a similar difficulty.” Chollet posed a set of problems, each of which requires an AI programme to arrange colored squares on a grid (格栅) based on just a few prior examples. It’s not hard for a person. But modern machine-learning programmes-trained on huge amounts of data — cannot learn from so few examples.
Josh Tenenbaum, a professor in MIT's Center for Brains, Minds & Machines, works closely with Spelke and uses insights from cognitive science as inspiration for his programmes. He says much of modern AI misses the bigger picture, comparing it to a cartoon about a two-dimensional world populated by simple geometrical (几何形的) people. AI programmes will need to learn in new ways — for example, by drawing causal inferences rather than simply finding patterns. “At some point — you know, if you’re intelligent — you realize maybe there's something else out there,” he says.
1. Compared to an advanced AI programme, a baby might be better at _______________.| A．labeling images | B．identifying locations |
| C．playing games | D．making adjustments |
| A．Stimulating. | B．Measuring. | C．Beating. | D．Limiting. |
| A．AI is good at finding similar patterns |
| B．AI should gain abilities with less training |
| C．AI lacks the ability of generalizing a skill |
| D．AI will match humans in cognitive ability |
| A．What is exactly intelligence? |
| B．Why is modern AI advanced? |
| C．Where is human intelligence going? |
| D．How do humans tackle the challenge of AI? |
7 . To learn to think is to learn to question. Those who don't question never truly think for themselves. These are simple rules that have governed the advancement of science and human thought since the beginning of time. Advancements are made when thinkers question theories and introduce new ones. Unfortunately, it is often the great and respected thinkers who end up slowing the progress of human thought. Aristotle was a brilliant philosopher whose theories explained much of the natural world, often incorrectly. He was so esteemed by the scientific community that even 1，200 years after his death, scientists were still trying to build upon his mistakes rather than correct them!
Brilliant minds can intimidate upandcoming thinkers who are not confident of their abilities. They often believe they are inferior to the minds of giants such as Aristotle, leading many to accept current paradigms instead of questioning them.
I, like many thinkers of the past, once believed in my mental inferiority. I was certain that my parents, my teachers-adults in general-were always right. They were like a textbook to me; I didn't question what was written on those pages. I respected them, and accepted whatever they told me. But that attitude soon changed. My mind's independence was first stimulated in the classroom.
A stern, 65yearold elementaryschool science teacher once told me that light is a type of wave. I confidently went through years of school believing that light is a wave. One day，however I heard the German exchange student mention that light could be made up of particles. As the others laughed at his statement, I started to question my beliefs.
Maybe the teachers and textbooks hadn't given me the whole story. I went to the library, did some research and learned of the lightasawave versus lightasaparticle debate. I read about Einstein's discovery of the dual nature of light and learned the facts of a paradox(悖论) that puzzles the world's greatest thinkers to this day. Light behaves as both a particle and a wave, it is both at once. I realized I had gone through life accepting only half of the story as the whole truth.
Each new year brought more new facts, and I formulated even more questions. I found myself in the library after school, trying to find my own answers to gain a more complete understanding of what I thought I already knew. I discovered that my parents and teachers are incredible tools in my quest for knowledge, but they are never the final word. Even textbooks can be challenged. I learned to question my sources, I learned to be a thinker. I once believed that everything I learned at home and at school was certain, but I have now discovered to reexamine when necessary.
Questions are said to be the path to knowledge and truth, and I plan to continue questioning. How many things do we know for sure today that we will question in the future? At this moment, I know that our sun will burn for another five billion years, and I know nothing can escape the gravity of a black hole. This knowledge, however, may change in the next 20 years-maybe even in the next two. The one thing we can control now is our openness to discovery. Questions are the tools of open minds, and open minds are the key to intellectual advancement.
1. In the first paragraph, Aristotle is taken as an example to show that ______.| A．he is the greatest and respected philosopher of all time |
| B．huge influence of great thinkers may block human thought |
| C．advancements are made when thinkers question theories |
| D．great thinkers often make mistakes and then correct them |
| A．Frighten. | B．Encourage. | C．Strength. | D．Persuade. |
| A．what he learned from textbooks before turned out to be wrong |
| B．he was inspired by the different ideas from an exchange student |
| C．he was laughed at by other students for his unacceptable statement |
| D．he was not satisfied with his life and desperate to achieve success |
| A．looks down upon great thinkers all the time |
| B．never doubts what he has learned in the textbook |
| C．always throws himself into the laboratory |
| D．determines to be a thinker and questioner |
| A．the author is not quite sure about his future |
| B．we human beings don't dare to predict future |
| C．theory of black holes will change in two years |
| D．questioning is necessary to promote advancement |
| A．Following rules. | B．Challenging yourself. |
| C．Questioning giants. | D．Predicting future. |
8 . According to a new study， teens focus on rewards and have a hard time learning to avoid punishment or consider the consequences of alternative actions.
University College London researchers compared how teens and adults learn to make choices based on the available information. They tracked the way in which 18 volunteers aged 12-17 and 20 volunteers aged 18-32 completed tasks in which they had to choose between abstract symbols.
Each symbol was consistently associated with a fixed chance of a reward, punishment, or no outcome. As the trial progressed ， participants learned which symbols were likely to lead to each outcome and adjusted their choices accordingly. Teens and adults were equally good at learning to choose symbols associated with reward， but teens were less good at avoiding symbols associated with punishment. Adults also performed significantly better when they were told what would have happened if they had chosen the other symbol after each choice， while teens did not appear to take this information into account.
“From this experimental lab study we can draw conclusions about learning during the teen years. We find that teens and adults learn in different ways， something that might be relevant to education," said lead author Dr. Stefano Palminteri. " Unlike adults, teens are not so good at learning to adjust their choices to avoid punishment. This suggests that incentive systems based on reward rather than punishment may be more effective for this age group. Additionally, we found that teens did not learn from being shown what would have happened if they made alternative choices."
To interpret the results, the researchers developed computational models of learning and ran simulations （模拟）applying them to the results of the study. The first was a simple model, one that learned from rewards, and the second model added to this by also learning from the option that was not chosen. The third model was the most complete and took the full context into account, with equal weight given to punishment avoidance and reward seeking. For example, obtaining no outcome rather than losing a point is weighted equally to gaining a point rather than having no outcome.
Comparing the experimental data to the models, the team found that teens" behavior followed the simple reward-based model while adults" behavior matched the complete, contextual model. “Our study suggests that teens are more receptive to rewards than they are to punishments of equal value, ” said senior author Dr. Sarah-Jayne Blakemore. “As a result, it may be useful for parents and teachers to frame things in more positive terms.”
1. It can be learned from the study that .| A．adults made choices faster than teens |
| B．adults understood rewards better than teens |
| C．teens reacted better to reward than punishment |
| D．teens were aware of the outcome of each choice |
| A．They reflected people’s strong desire for punishment avoidance. |
| B．They gave circumstances different degrees of consideration. |
| C．They paid equal attention to reward and punishment. |
| D．They shaped the behavior of people at different ages. |
| A．accustomed | B．opposed |
| C．sympathetic | D．responsive |
| A．“If you insist on doing things in this way， you will lose ten points. " |
| B．“If we had talked about this earlier， you wouldn’t have made the mistake. " |
| C．“ If you hand in your assignment ahead of time， you will get an extra bonus." |
| D．“If you want to approach a problem differently ， you can talk to your parents. " |
9 . As the effects of climate change become more disastrous, well-known research institutions and government agencies are focusing new money and attention on an idea: artificially cooling the planet, in the hopes of buying humanity more time to cut greenhouse gas emissions.
That strategy, called solar climate intervention (干预) or solar geoengineering, involves reflecting more of the sun’s energy back into space — abruptly reducing global temperatures in a way that imitates the effects of ash clouds flowing out from the volcanic eruptions. The idea has been considered as a dangerous and fancied solution, one that would encourage people to keep burning fossil fuels while exposing the planet to unexpected and potentially threatening side effects, producing more destructive hurricanes, wildfires floods and other disasters.
But. as global warming continues, producing more destructive hurricanes, wildfires floods and other disasters, some researchers and policy experts say that concerns about geoengineering should be outweighed by the imperative to better understand it, in case the consequence of climate change become so terrible that the world can’t wait for better solutions.
One way to cool the earth is by injecting aerosols (气溶胶) into the upper layer of the atmosphere. where those particles reflect sunlight away from the earth. That process works, according to Douglas MacMartin, a researcher at Cornell University.
“We know with 100% certainty that we can cool the planet,” he said in an interview. What’s still unclear, he added, is what happens next. Temperature, MacMartin said, is an indicator for a lot of climate effects. “What does it do to the strength of hurricanes?” he asked, “What does it do to agriculture production? What does it do to the risk of forest fires?”
Another institution funded by the National Science Foundation will analyze hundreds of simulations of aerosol injection, testing the effects on weather extremes around the world. One goal of the research is to look for a sweet spot: the amount of artificial cooling that can reduce extreme weather events without causing broader changes in regional rainfall patterns or similar impacts.
1. Why do researchers and government agencies work on cooling the earth?| A．To prevent natural disasters. | B．To win more time to reduce gas emissions. |
| C．To imitate volcanic eruptions. | D．To encourage more people to bur fossil fuels. |
| A．More volcanoes will throw out. |
| B．More solar energy will go into space. |
| C．More disasters will endanger the future of the world. |
| D．People will keep burning fossil fuels to keep warm. |
| A．He thinks more research remains to be done. |
| B．He is optimistic about the effect of cooling the earth. |
| C．He is concerned about the reduction in agriculture production. |
| D．He disapproves of the practice of solar climate intervention. |
| A．The rainfall pattern of a region. |
| B．The modest drop in temperature. |
| C．The number of extreme weather events. |
| D．The injection amount of aerosol. |
10 . There is more that comes with older age than greying hair and wrinkled skin When humans reach their later years, they favour more established friends and their social circle is reduced.
Now, for what appears to be the first time, scientists have seen the same behaviour in another species. Twenty years of observations of chimpanzees (猩猩) reveal that older males choose to hang out with their long-term friends at the expense of other relationships.
The researchers studied 78, 000 hours of observations made between 1996 and 2016 that followed the social interactions of 21 male chimpanzees between the ages of 15 and 58 years old. They classified the chimps’ relationships depending on the amount of time they sat with others and groomed (梳毛) them. They then rated the various pairings as mutual (相互的) friendships, where both chimps seemed to enjoy the relationship; one-sided friendships, where one chimp was more keen to be friends than the other; and non-friendships, where neither chimp showed interest in the other.
When the scientists looked at the patterns of friendships, they found that the older chimps had more mutual friendships and fewer one-sided friendships than younger chimps. Another feature seen in older humans was also spotted in the chimps. As the males got older, their levels of aggression (挑衅) tailed off, meaning they started fewer fights and tended to intimidate others in their group less often.
The observations have left the researchers puzzled. According to an idea in psychology known as socioemotional selectivity theory, or SST, older humans prefer more positive relationships because they are aware time is running out. But many animal experts argue that chimpanzees lack the human sense of mortality (死亡), suggesting something else is driving the behaviour.
Robin Dunbar, a professor of evolutionary psychology at the University of Oxford, said in humans, the decline in social circles with age is due to declining social motivation to get out and meet people combined by lack of opportunity. In chimpanzees, as older males compete less for mates, they may focus on close, reciprocal (互惠的) relationships with trusted partners, she said.
1. What do older male chimpanzees favour?| A．Old friendships. | B．New bonds. |
| C．Greying hair. | D．Wrinkled skin. |
| A．By turning to other scientists. |
| B．By introducing a new concept. |
| C．By forming relationships with them. |
| D．By analyzing two decades’ observations. |
| A．Threaten. | B．Motivate. | C．Defend. | D．Accompany. |
| A．Awareness of time. | B．Less competition for mates. |
| C．Low motivation for socialization. | D．Lack of the human sense of mortality. |
