单选题 广告的基本功能即传达信息。如果想告诉某人某件事，你必须引起他的兴趣和注意，这是人际交往、大众传播(mass-communication)中的一个真理。将观众的注意力吸引过来，广告才能实现说服他们相信某个观点的功能。因为名人的知名度，名人广告能轻松地把观众的注意力杂乱的环境中吸引过来，让产品和广告成为大众关注的中心。本来大家并不了解的一个品牌，因为名人的关系随即受到重视，在繁杂的信息中脱颖而出，快速提升产品的知名度。

单选题Research on animal intelligence always makes us wonder just how smart humans are. Consider the fruit-fly experiments described by Carl Zimmer in the Science Times. Fruit flies who were taught to be smarter than the average fruit fly 26 to live shorter lives. This suggests that dimmer bulbs burn longer, that there is a(n) 27 in not being too bright. Intelligence, it turns out, is a high-priced 28 . It takes more upkeep, burns more fuel and is slow off the starting line because it depends on learning—a(n) 29 process—instead of instinct. Plenty of other species are able to learn, and one of the things they've apparently learned is when to stop. Is there an adaptive value to limited intelligence? That's the question behind this new research. Instead of casting a wistful glance 30 at all the species we've left in the dust I.Q.-wise, it implicitly asks what the real costs of our own intelligence might be. This is on the 31 of every animal we've ever met. Research on animal intelligence also makes us wonder what experiments animals would 32 on humans if they had the chance. Every cat with an owner, for instance, is running a small-scale study in operant conditioning. We believe that if animals ran the labs, they would test us to 33 the limits of our patience, our faithfulness, our memory for locations. They would try to decide what intelligence in humans is really for, not 34 how much of it there is. Above all, they would hope to study a 35 question: Are humans actually aware of the world they live in? So far the results are inconclusive. A. mind E. advantage I. aptly M. tended B. fundamental F. happened J. overcome N. inclination C. gradual G. spontaneous K. option O. perform D. determine H. backward L. merely

单选题 Now listen to the following recording and answer questions22-24.

单选题Teachers need to be aware of the emotional, intellectual, and physical changes that young adults experience. And they also need to give serious thought to how they can best 27 such changes. Growing bodies need movement and 28 , but not just in ways that emphasize competition. Because they are adjusting to their new bodies and a whole host of new intellectual and emotional challenges, teenagers are especially serf-conscious and need the confidence that comes from achieving success and knowing that their accomplishments are 29 by others. However, the 30 teenage lifestyle is already filled with so much competition that it would be wise to plan activities in which there are more winners than losers, for example, publishing newsletters with many student-written book reviews, 31 student artwork, and sponsoring book discussion clubs. A variety of small clubs can provide 32 opportunities for leadership, as well as for practice in successful group 33 . Making friends is extremely important to teenagers, and many shy students need the security of some kind of organization with a supportive adult 34 visible in the background. In these activities, it is important to remember that young teens have short attention spans. A variety of activities should be organized so that participants can remain active as long as they want and then go on to something else without feeling 35 and without letting the other participants down. This does not mean that adults must accept irresponsibility. On the contrary, they can help students acquire a sense of 36 by planning for roles that are within their capabilities and their attention spans and by having clearly stated rules. A. dynamics E. displaying I. admired M. accommodate B. multiple F. rarely J. nutrition N. barely C. guidance G. exercise K. commitment O. claimed D. typical H. guilty L. surplus

单选题Go (围棋) is an ancient Asian game. In recent years, computer experts, particularly those 27 in artificial intelligence, have felt the fascination. Programming other board games has been a relative snap. Even chess has 28 to the power of the processor. Five years ago, a chess-playing computer called Deep Blue not only beat but thoroughly 29 Garry Kasparov, the world champion at that time. That is because chess, while highly complex, can be reduced to a matter of brute force computation. Go is different. Deceptively easy to learn, either for a computer or a human, it is a game of such depth and 30 that it can take years for a person to become a strong player. To date, no computer has been able to achieve a skill level beyond that of the casual player. The game is played on a board divided into a grid of 19 31 and 19 vertical lines. Black and white pieces called stones are placed one at a time on the grid's intersections. The object is to acquire and defend 32 by surrounding it with stones. Programmers working on Go see it as more accurate than chess in 33 the ways the human mind works. The challenge of programming a computer to mimic that process goes to the core of artificial intelligence, which involves the study of learning and decision-making, strategic thinking, knowledge representation, pattern recognition and perhaps most intriguingly, intuition. In the 34 of a chess game, a player has an average of 25 to 35 moves available. In Go, on the other hand, a player can choose from an average of 240 moves. A Go-playing computer would need about 30000 years to look as far ahead as Deep Blue can with chess in three seconds. But the 35 go deeper than processing power. Not only do Go programs have trouble evaluating positions quickly; they have trouble making it correctly. 36 , the allure (吸引力) of computer Go increases as the difficulties it poses encourages programmers to advance basic work in artificial intelligence. A. complexity B. Consequently C. course D. horizontal E. humbled F. humiliated G. Nonetheless H. obstacles I. reflecting J. responding K. slanted L. specializing M. submitted N. subscribed O. territory

单选题 Questions2-5 are based on the conversation you have just heard.

单选题 Grow Plants Without Water A. Ever since humanity began to farm our own food, we've faced the unpredictable rain that is both friend and enemy. It comes and goes without much warning, and a field of lush (茂盛的) leafy greens one year can dry up and blow away the next. Food security and fortunes depend on sufficient rain, and nowhere more so than in Africa, where 96% of farmland depends on rain instead of the irrigation common in more developed places. It has consequences: South Africa's ongoing drought—the worst in three decades—will cost at least a quarter of its corn crop this year. B. Biologist Jill Farrant of the University of Cape Town in South Africa says that nature has plenty of answers for people who want to grow crops in places with unpredictable rainfall. She is hard at work finding a way to take traits from rare wild plants that adapt to extreme dry weather and use them in food crops. As the earth's climate changes and rainfall becomes even less predictable in some places, those answers will grow even more valuable. 'The type of farming I'm aiming for is literally so that people can survive as it's going to get more and more dry,' Farrant says. C. Extreme conditions produce extremely tough plants. In the rusty red deserts of South Africa, steep-sided rocky hills called inselbergs rear up from the plains like the bones of the earth. The hills are remnants of an earlier geological era, scraped bare of most soil and exposed to the elements. Yet on these and similar formations in deserts around the world, a few fierce plants have adapted to endure under ever-changing conditions. D. Farrant calls them resurrection plants (复苏植物). During months without water under a harsh sun, they wither, shrink and contract until they look like a pile of dead gray leaves. But rainfall can revive them in a matter of hours. Her time-lapse (间歇性拍摄的) videos of the revivals look like someone playing a tape of the plant's death in reverse. E. The big difference between 'drought-tolerant' plants and these tough plants: metabolism. Many different kinds of plants have developed tactics to weather dry spells. Some plants store reserves of water to see them through a drought; others send roots deep down to subsurface water supplies. But once these plants use up their stored reserve or tap out the underground supply, they cease growing and start to die. They may be able to handle a drought of some length, and many people use the term 'drought tolerant' to describe such plants, but they never actually stop needing to consume water, so Farrant prefers to call them drought resistant. F. Resurrection plants, defined as those capable of recovering from holding less than 0.1 grams of water per gram of dry mass, are different. They lack water-storing structures, and their existence on rock faces prevents them from tapping groundwater, so they have instead developed the ability to change their metabolism. When they detect an extended dry period, they divert their metabolisms, producing sugars and certain stress-associated proteins and other materials in their tissues. As the plant dries, these resources take on first the properties of honey, then rubber, and finally enter a glass-like state that is 'the most stable state that the plant can maintain,' Farrant says. That slows the plant's metabolism and protects its dried-out tissues. The plants also change shape, shrinking to minimize the surface area through which their remaining water might evaporate. They can recover from months and years without water, depending on the species. G. What else can do this dry-out-and-revive trick? Seeds—almost all of them. At the start of her career, Farrant studied 'recalcitrant seeds (顽拗性种子),' such as avocados, coffee and lychee. While tasty, such seeds are delicate—they cannot bud and grow if they dry out (as you may know if you've ever tried to grow a tree from an avocado pit). In the seed world, that makes them rare, because most seeds from flowering plants are quite robust. Most seeds can wait out the dry, unwelcoming seasons until conditions are right and they sprout (发芽). Yet once they start growing, such plants seem not to retain the ability to hit the pause button on metabolism in their stems or leaves. H. After completing her Ph.D. on seeds, Farrant began investigating whether it might be possible to isolate the properties that make most seeds so resilient (迅速恢复活力的) and transfer them to other plant tissues. What Farrant and others have found over the past two decades is that there are many genes involved in resurrection plants' response to dryness. Many of them are the same that regulate how seeds become dryness-tolerant while still attached to their parent plants. Now they are trying to figure out what molecular signaling processes activate those seed-building genes in resurrection plants—and how to reproduce them in crops. 'Most genes are regulated by a master set of genes,' Farrant says. 'We're looking at gene promoters and what would be their master switch.' I. Once Farrant and her colleagues feel they have a better sense of which switches to throw, they will have to find the best way to do so in useful crops. 'I'm trying three methods of breeding,' Farrant says: conventional, genetic modification and gene editing. She says she is aware that plenty of people do not want to eat genetically modified crops, but she is pushing ahead with every available tool until one works. Farmers and consumers alike can choose whether or not to use whichever version prevails: 'I'm giving people an option.' J. Farrant and others in the resurrection business got together last year to discuss the best species of resurrection plant to use as a lab model. Just like medical researchers use rats to test ideas for human medical treatments, botanists use plants that are relatively easy to grow in a lab or greenhouse setting to test their ideas for related species. The Queensland rock violet is one of the best studied resurrection plants so far, with a draft genome (基因图谱) published last year by a Chinese team. Also last year, Farrant and colleagues published a detailed molecular study of another candidate, Xerophyta viscosa, a tough-as-nail South African plant with lily-like flowers, and she says that a genome is on the way. One or both of these models will help researchers test their ideas—so far mostly done in the lab—on test plots. K. Understanding the basic science first is key. There are good reasons why crop plants do not use dryness defenses already. For instance, there's a high energy cost in switching from a regular metabolism to an almost-no-water metabolism. It will also be necessary to understand what sort of yield farmers might expect and to establish the plant's safety. 'The yield is never going to be high,' Farrant says, so these plants will be targeted not at Iowa farmers trying to squeeze more cash out of high-yield fields, but subsistence farmers who need help to survive a drought like the present one in South Africa. 'My vision is for the subsistence farmer,' Farrant says. 'I'm targeting crops that are of African value.'

单选题 As the economic role of multinational, global corporations expands, the international economic environment will be shaped increasingly not by governments or international institutions, but by the interaction between governments and global corporations, especially in the United States, Europe, and Japan. A significant factor in this shifting world economy is the trend toward regional trading blocs of nations, which has a potentially large effect on the evolution of the world trading system. Two examples of this trend are the United, States, Canada Free Trade Agreement (FTA. and Europe 1992, the move by the European Community (EC. to dismantle impediments to the free flow of goods, services, capital, and labor among member states by the end of 1992. However, although numerous political and economic factors were operative in launching the move to integrate the EC's markets, concern about protectionism within the EC does not appear to have been a major consideration. This is in sharp contrast to the FTA, the overwhelming reason for that bilateral initiative was fear of increasing United States protectionism. Nonetheless, although markedly different in origin and nature, both regional developments are highly significant in that they will foster integration in the two largest and richest markets of the world, as well as provoke question about the future direction of the world trading system.

单选题 西湖三面环山，湖区内有大量的寺庙、古塔(pagoda)、园林和人造岛，它是中国同林设计师的重要灵感来源。

单选题 How Girls Can Win in Math and Science A. Math is a cumulative subject, unlike say history, which can be learned in discrete units. College algebra (代数) is basically a course in the language of mathematics. Some might say that algebra is the mechanics of mathematics. The examples included at this level are simple, designed to reinforce that the student has learned the 'how'. The next layer of courses teaches how to use this language, or this set of tools, to describe and model the real world. Being able to do this should leave no doubt in the student's mind that they are mathematically competent. B. For years, feminists have lamented (悲叹) the sorry state of girls in math and science, as they lag behind their male peers in test scores and shy away from careers in engineering and technology. Yet perhaps the most frustrating recent development on the topic is that some of the very programs designed to help girls get ahead may be holding them back or are simply misguided. Take single-sex math and science classes. While they seem like a logical way to give girls ajump-start in these subjects, new research suggests this initiative— championed over the past two decades as a possible solution—may backfire. C. In a study published last year, psychology Howard Glasser at Bryn Mawr College examined teacher-student interaction in sex-segregated science classes. As it turned out, teachers behaved differently toward boys and girls in a way that gave boys an advantage in scientific thinking. While boys were encouraged to engage in back and-forth questioning with the teacher andfellow students, girls had many fewer such experiences. Glasser suggests they didn't learn to argue in the same way as boys, and argument is the key to scientific thinking. Glasser pointsout that sex segregated classrooms can construct differences between the sexes by giving them unequal experiences. Unfortunately, such differences can impact kids' choices about future courses and careers. It's worth noting that the girls and boys in these science classes had similar grades, which masked the uneven dynamic. It was only when researchers reviewed videotapes of the lessons that they got a deeper analysis of what was actually going on, and what the kids were really learning. D. Glasser's research got a boost last September when the journal Science published a snatching (尖刻的) report on the larger issue of single-sex education, titled 'The Pseudoscience of Single-Sex Schooling'. In the article, eight leading psychologists and neuroscientists debunked (揭穿真相) research supporting single-sex education, and argued that sex segregation 'increases gender stereotyping and legitimizes institutional sexism'. E. Another misguided—or, mistimed—effort to improve girls' performance is the 'you can do it' messaging directed toward girls in middle school, the period when their scores start lagging. New research shows that even when preteen girls say they believe this message, 'stereotype threat'—when negative cultural stereotypes affect a group's behavior—has a dampening effect on their actual performance. F. In a 2009 study, psychologist Pascal Huguet of France's Aix-Marseille University found that middle-school girls scored highest on tests measuring visual-spatial abilities—which are key to success in engineering, chemistry, medicine, and architecture, fields that promise high-paying, prestigious jobs down the road—when they were led to believe that there were no gender differences on the tasks. Not surprisingly, when they were told that boys do better on these tasks, they did poorly. But curiously, when they were given no information, allowing cultural stereotypes to operate, they also did poorly. The stereotypes were already firmly established. The authors discovered: By middle school it's too little, too late. G. To disarm stereotypes, we must actively arm girls against them—starting at a very young age. By first or second grade, both girls andboyshave the notion that math is a 'boy thing'. But a 2011 study by psychologist Anthony Greenwald of the University of Washington found that there's a window of opportunity during these early years in which, while girls do see math largely as a male preserve, they haven't yet made the connection that 'because I am a girl, math is not for me'. During this short period, girls are relatively open to the idea that they can enjoy and do well at math. H. One strategy? Researchers suggest we take gender out of the equation in teaching about occupations. Rather than saying 'girls can be scientists', we should talk about what scientists do. For example, kids may be especially interested to know that scientists study how the world around them really works. Psychologists Rebecca Bigler of the University of Texas at Austin and Lynn Liben at Penn State say that when girls are encouraged to think this way, they're much more likely to retain what they're taught than they would be if they were just given the generic 'girls can do science' message. I. Finally, while women teachers can lead the way for girls in math and science, acting as role models, parents should be on the lookout for teachers' math anxiety. A 2010 study of first-and second-graders led by psychologist Sian L. Beilock at the University of Chicago found that girls may learn to fear math from their earliest instructors—and that female elementary-school teachers who lack confidence in their own math skills could be passing their anxiety along to their students. The more anxious teachers were about their own skills, the more likely their female students were to agree that 'boys are good at math and girls are good at reading'. And according to Beilock, elementary-education majors at the college level have the highest math anxiety level of any major, and may be unwittingly passing along a virus of underachievement to girls. J. Parents can 'vaccinate' girls against their teachers, math anxiety, according to new research. But there may be a silver lining to this story for parents. Even if your daughter has a teacher with high math anxiety, it's not inevitable that she's going to experience problems with math—it turns out that parents (or others) can 'vaccinate' girls against their teachers' qualms (不安). Beilock found that teachers' anxiety alone didn't do the damage. If girls already had a belief that 'girls aren't good at math', their achievement suffered. But the girls who didn't buy into that stereotype, who thought, of course I can be good at math, didn't tumble into an achievement gulf. K. Now that we have reason to believe that gender stereotyping starts much earlier than previously thought, we also need to accept that countering it requires more sophisticated approaches than those we now use. If girls continue to lag behind in math areas, our future economy and competitiveness could suffer. It's critical that we start our efforts in the primary grades and look beyond the obvious to succeed. If we look 'under the hood' at what's really going on with girls, instead of just skimming the surface, we can provide more than mere cosmetic solutions.

单选题 It's Time to Pay Attention to Sleep, the New Health Frontier A. Your doctor could soon be prescribing crucial sleep as treatment for everything from obesity to mental health as experts say carving out time for sleep is just as important as diet and exercise. B. After being diagnosed with brain and lung cancer in 2011, Lynn Mitchell, 68, was averaging about an hour of solid sleep a night. Stressed about her treatments, she was paying for it in hours of lost sleep. The brain cancer was already affecting her mobility—Mitchell was often dizzy and would lose her balance—but the lack of sleep was making things worse. Even walking became increasingly difficult. Exhausted in the mornings, she was practically incoherent. When her doctors recommended she see a sleep therapist, Mitchell was relieved at how benign it sounded in comparison to the chemotherapy (化疗) she had undergone, which had side effects like nausea and fatigue. C. For about nine weeks, Mitchell worked with the sleep therapist to adjust her sleep habits. She got under the covers only when she was extremely tired. She quit watching TV in bed. She stopped drinking caffeinated coffee in the evening. She also learned breathing exercises to relax and help her drift off. It was all quite simple and common sense, and, most importantly, noninvasive and didn't require popping any pills. D. 'It's common knowledge that sleep is needed for day-to-day function,' says Dr. David Rapoport, director of the Sleep Medicine Program at NYU School of Medicine. 'What isn't common knowledge is that it really matters—it's not just cosmetic.' Rapoport has long seen people seek sleep therapy because they're chronically tired or suffering from insomnia (失眠), but an increasing number of patients are being referred to his center for common diseases, disorders, and mental health. E. Researchers have known for some time that sleep is critical for weight maintenance and hormone balance. And too little sleep is linked to everything from diabetes to heart disease to depression. Recently, the research on sleep has been overwhelming, with mounting evidence that it plays a role in nearly every aspect of health. Beyond chronic illnesses, a child's behavioral problems at school could be rooted in mild sleep apnea (睡眠呼吸中止症). And studies have shown children with ADHD (注意力缺损多动障碍) are more likely to get insufficient sleep. A recent study published in the journal SLEEP found a link between older men with poor sleep quality and cognitive decline. Another study out this week shows sleep is essential in early childhood for development, learning, and the formation and retention of memories. Dr. Allan Rechtschaffen, a pioneer of sleep research at the University of Chicago, once said, 'If sleep does not serve an absolutely vital function, then it is the biggest mistake the evolutionary process ever made.' F. But to many of us, sleep is easily sacrificed, especially since lack of it isn't seen as life threatening. Over time, sleep deprivation can have serious consequences, but we mostly sacrifice a night of sleep here and there, and always say that we'll 'catch up'. Luckily, it is possible to make up for sleep debt (though it can take a very long time), but most Americans are still chronically sleep deprived. G. While diet and exercise have been a part of public health messaging for decades, doctors and health advocates are now beginning to argue that getting quality sleep may be just as important for overall health. 'Sleep is probably easier to change than diet or exercise,' says Dr. Michael Grandner, a sleep researcher at the University of Pennsylvania. 'It may also give you more of an immediate reward if it helps you get through your day.' And while there's more evidence linking diet and exercise as influential health factors, sleep is probably more important in terms of brain and hormonal function, Grandner says. 'Among a small group of sleep researchers, if it is always been said that eating, exercise, and sleep are the three pillars of health,' says Dr. Rapoport. H. In our increasingly professional and digital lives, where there are now more things than ever competing for the horns in our day, carving out time for sleep is not only increasingly difficult, but also more necessary. Using technology before bed stimulates us and interferes with our sleep, yet 95% of Americans use some type of electronics like a computer, TV, or cell phone at least a few nights a week within the hour before we go to bed, according to a 2011 National Sleep Foundation survey. 'Many doctors, lawyers, and executives stay up late and get up early and burn the candle at both ends,' says Dr. Richard Lang, chair of Preventative Medicine at the Cleveland Clinic. 'Making sure they pay attention to sleep in the same way they pay attention to diet and exercise is crucial.' I. To some, sleep has become a powerful medicine to mental health. Arianna Huffington, president and editor-in-chief of the Huffington Post Media Group, advocates that sleep is the secret to success, happiness, and peak performance. After passing out a few years ago from exhaustion and cracking a cheekbone (颧骨) against her desk, Huffington has become something of a sleep promoter. In a 2010 TED Women conference, Huffington said, 'The way to a more productive, more inspired, more joyful life is getting enough sleep.' Research linking high-quality sleep with better mental health is growing; a 2013 study found that treating depressed patients for insomnia can double their likelihood of overcoming the disorder. J. While 70% of physicians agree that inadequate sleep is a major health problem, only 43% counsel their patients on the benefits of adequate sleep. But there's growing pressure on primary care physicians to address, and even prescribe, sleep during routine check-ups. In a recent study published in the journal The Lancet Diabetes Endocrinology, the researchers concluded that health professionals should prescribe sleep to prevent and treat metabolic disorders like obesity and diabetes. And overlooking sleep as a major health issue can also have deadly consequences. It was recently reported that the operator of the Metro-North train that derailed in New York last year, killing four people and injuring more than 70, had an undiagnosed case of sleep apnea. K. Sleep therapies can range from simply learning new lifestyle behaviors to promote sleep, to figuring out how to position oneself in bed. More drastic measures involve surgery to open up an airway passage for people suffering from disorders like sleep apnea. Sleeping pills can be prescribed too, to get much needed rest, but sleep therapists tend to favor other approaches because of possible dependencies developing. L. A large part of reaping the benefits of sleep is known when you're not getting the right amount. According to a 2013 Gallup survey, 40% of Americans get less than the recommended seven to eight hours a night. While the typical person still logs about 6-8 hours of sleep per night, that's a drop from the 7.9 Americans were getting in the 1940s. M. When it comes to adequate sleep, it's much more personalized than previously thought. Some people feel great on five hours of rest, while others need ten. The best way to determine if you're getting the right amount, doctors say, is to find out how many hours of sleep you need to be able to wake up without an alarm and feel rested, refreshed, and energetic throughout the day. N. Since reforming her sleep habits, Mitchell has been clocking up to seven hours of sleep a night for the past two months. 'I'm alert in the morning, my balance is better, and I feel peppier,' says Mitchell. Getting enough sleep has helped her better deal with her cancers, and its symptoms. The best news is that she recently found out that her brain tumor is shrinking, and there are fewer cancerous spots on her lungs.

单选题 Blood vessels running all through the lungs carry blood to each air sac (囊), or alveolus(肺泡), and then back again to the heart. Only the thin wall of the air sac and the thin wall of a capillary (毛细血管) are between the air and the blood. So oxygen easily diffuses from the air sacs through the walls into the blood, while carbon dioxide easily diffuses from the blood through the walls into the air sacs. When blood is sent to the lungs by the heart, it has come back from the cells in the rest of the body. So the blood that goes into the wall of an air sac contains much dissolved carbon dioxide but very little oxygen. At the same time, the air that goes into the air sac contains much oxygen but very little carbon dioxide. You have learned that dissolved materials always diffuse from where there is more of them to where there is less. Oxygen from the air dissolves in the moisture on the lining of the air sac and diffuses through the lining into the blood. Meanwhile, carbon dioxide diffuses from the blood into the air sac. The blood then flows from the lungs back to the heart, which sends it out to all other parts of the body. Soon after air goes into an air sac, it gives up some of its oxygen and takes in some carbon dioxide from the blood. To keep diffusion going as it should, this carbon dioxide must be gotten rid of. Breathing, which is caused by movements of the chest, forces the used air out of the air sacs in your lungs and brings in fresh air. The breathing muscles are controlled automatically so that you breathe at the proper rate to keep your air sacs supplied with fresh air. Ordinarily, you breathe about twenty-two times a minute. Of course, you breathe faster when you are exercising and slower when you are resting. Fresh air is brought into your lungs when you breathe in, or inhale(吸入), while used air is forced out of your lungs when you breathe out, or exhale. Some people think that all the oxygen is taken out of the air in the lungs and that what we breathe out is pure carbon dioxide. But these ideas are not correct. Air is a mixture of gases that is mostly nitrogen (氮). This gas is not used in the body. So the amount of nitrogen does not change as air is breathed in and out. But while air is in the lungs, it is changed in three ways: (1) About one-fifth of the oxygen in the air goes into the blood. (2) An almost equal amount of carbon dioxide comes out of the blood into the air. (3) Moisture from the linings of the air passages and air sacs evaporates until the air is almost saturated.