阅读理解What is the finding of the new study?

阅读理解Wise buying is a positive way in which you can make your money go fuller

阅读理解When Katherine Goldstein was (47) up in the suburbs of Washington, D. C. , her mom, an artist, was usually home waiting for her after school. Goldstein, now twenty six, is (48) that her mother was around. But she plans to do things (49) . A recent graduate of Harvard Law School, Goldstein works as a clerk for a circuit court judge in Cleveland and is engaged to be married in October. "I (50) having a full-time job and children as an eventuality and a (51) ," she says. Already she is (52) what it will take to combine a law career with raising a family. Her (53) : tackle the more (54) facets of her profession--like trial law--now, before she starts having kids. That way, "I can transition to a more family-friendly role when I have children," she explains. She has been deeply (55) by one of her "mentors," a law partner in her mid 30s who recently gave birth to her first child. "She told me that when she dies, she just wants to say that she was a good wife and mother," says Goldstein "It''s less important to her to become a (56) judge or a fearsome trial lawyer. I find that advice really useful." WORD BANK A) bringing I) reality B) view J) scene C) totally K) growing D) calculation L) influenced E) provincial M) differently F) federal N) anticipating G) demanding O) grateful H) career

阅读理解Scratchy throats, stuffy noses and body aches all spell misery, but being able to tell if the cause is a cold or flu (流感) may make a difference in how long the misery lasts. The American Lung Association (ALA) has issued new guidelines on combating colds and the flu, and one of the keys is being able to quickly tell the two apart. That''s because the prescription drugs available for the flu need to be taken soon after the illness sets in. As for colds, the sooner a person starts taking over-the-counter remedy, the sooner relief will come. The common cold and the flu are both caused by viruses. More than 200 viruses can cause cold symptoms, while the flu is caused by three viruses -- flu A, B and C. There is no cure for either illness, but the flu can be prevented by the flu vaccine (疫苗) , which is, for most people, the best way to fight the flu, according to the ALA. But if the flu does strike, quick action can help. Although the flu and common cold have many similarities, there are some obvious signs to look for. Cold symptoms such as stuffy nose, runny nose and scratchy throat typically develop gradually, and adults and teens often do not get a fever. On the other hand, fever is one of the characteristic features of the flu for all ages. And in general, flu symptoms including fever and chills, sore throat and body aches come on suddenly and are more severe than cold symptoms. The ALA notes that it may be particularly difficult to tell when infants and preschool age children have the flu. It advises parents to call the doctor if their small children have flu-like symptoms. Both cold and flu symptoms can be eased with over-the-counter medications as well. However, children and teens with a cold or flu should not take aspirin for pain relief because of the risk of Reye syndrome (综合症), a rare but serious condition of the liver and central nervous system. There is, of course, no vaccine for the common cold. But frequent hand washing and avoiding close contact with people who have colds can reduce the likelihood of catching one.

阅读理解It is hard to track the blue whale, the ocean''s largest creature, which has almost been killed off by commercial whaling and is now listed as an endangered species. Attaching radio devices to it is difficult, and visual sightings are too unreliable to give real insight into its behavior. So biologists were delighted early this year when, with the help of the Navy, they were able to track a particular blue whale for 43 days, monitoring its sounds. This was possible because of the Navy''s formerly top-secret system of underwater listening devices spanning the oceans. Tracking whales is but one example of an exciting new world just opening to civilian scientists after the cold war as the Navy starts to share and partly uncover its global network of underwater listening system built over the decades to track the ships of potential enemies. Earth scientists announced at a news conference recently that they had used the system for closely monitoring a deep-sea volcanic eruption (爆发) for the first time and that they plan similar studies. Other scientists have proposed to use the network for tracking ocean currents and measuring changes in ocean and global temperatures. The speed of sound in water is roughly one mile a second -- slower than through land but faster than through air. What is most important, different layers of ocean water can act as channels for sounds, focusing them in the same way a stethoscope (听诊器) does when it carries faint noises from a patient''s chest to a doctor''s ear. This focusing is the main reason that even relatively weak sounds in the ocean, especially low-frequency ones, can often travel thousands of miles.

阅读理解The three main types of secondary education in the United States have been provided by the Latin grammar school, the academy, and the public high school. The first of these was a colonial institution. It began in New England with the establish ment in 1635 of the Boston Free Latin School. The curriculum (课程) consisted mainly of the classical languages, and the purpose of this kind of school was the preparation of boys for college, where most of them would be fitted for the ministry. The academy began in the early 1750''s with Benjamin Franklin''s school in Philadelphia, which later became the University of Pennsylvania. It extended generally to about the middle nineteenth century, except in the southern states where the public high school was late in developing and where the academy continued to be a principal means of secondary education even after 1900. The academy was open to girls as well as to boys, and it provided a wider curriculum than what the Latin grammar school had furnished. It was designed not only as a preparation for college but also for practical life in commercial and business activities. Although its wide educational values are evident and are recognized as important contributions to secondary education in this country, the academy has never been considered a public institution as the public high school has come to be. The public high school had its origin in Massachusetts in 1821 when the English Classical School was established in Boston. In 1827, the state enacted(制定) the first state-wide public high-school law in the United States. By 1840, there were perhaps a dozen public high schools in Massachusetts and many in other eastern states by 1850, they could also be found in many other states. Just as the curriculum of the academy grew out of that of the Latin grammar school, the curriculum of the public high school developed out of that of the academy. The public high school in the United States is a repudiation (推翻) of the aristocratic(贵族的)and selective principle of the European educational tradition. Since 1890, enrollments (入学) in secondary schools, mainly public high schools, have practically doubled in this country every ten years.

阅读理解To most Africans, tribalism simply means very strong loyalty to one''s ethnic group. It is a force that can be both good and bad. By definition tribalism means sharing among members of the extended family. It makes sure that a person is taken care of by his own group. To give a job to a fellow tribesman is not wrong; it is an obligation. Similarly ,for a politician or military leader it is considered good common sense to choose his closest adviser from people of his own tribe. This ensures security, continuity, authority. Tribal loyalty may mean a quick promotion--from sergeant to captain, from clerk to manager--within a very short time. Modern African politicians publicly speak out against tribal divisions. Yet it remains perhaps the most powerful force in day-to-day African life. As evidence of tribalism, in 1977 in Kenya, president Jomo Kenyatta''s tribe controlled business and politics. Eight of the 21 cabinet posts, including the most important four were filled. by Kikuyus. In Uganda in the same year, the president'' s small Kakwa tribe filled almost all the highest government and military positions! In Agola, Ethiopia, and Nigeria, the fighting in the past ten years can be partly explained by disagreements among tribes.

阅读理解You are busy filling out the application form for a position you really need. Let''s assume you once actually completed a couple of years of college work or even that you completed your degree. Isn''t it tempting to lie just a little, to claim on the form that your diploma represents a Harvard degree? Or that you finished an extra couple of years back at State University? More and more people are resorting to outright deception like this to land their first job or to move ahead in their careers, for personnel officers, like most Americans, value degrees from prestige schools. A job applicant may have a good education anyway , but he or she assumes that chances of being hired are better with a diploma from a well-known university. Registrars at most well-known colleges say they deal with fraudulent claims like these at the rate of about one per week. Personnel officers do check up on degrees listed on application forms. Then, if it turns out that an applicant is lying, most colleges are reluctant to accuse the applicant directly. One Ivy League school calls them "impostors" ; another refers to them as "special cases". One well-known West Coast school, in perhaps the most delicate phrase of all, says that these claims are made by "no such people". To avoid outright lies, some job-seekers claim that they "attended" or "were associated with" a college or university. After carefully checking, a personnel officer may discover that "attending" means flunking out after one semester. It may be that " being associated with" a college means that the job-seeker visited his younger brother for a football weekend. One school that keeps records of false claims says that the practice dates back at least to the turn of the century—that''s when they began keeping records, anyhow. If you don''t want to lie or even stretch the truth, there are companies that will sell you a phoney diploma. One company, with offices in New York and on the West Coast, will put your name on a diploma from any number of nonexistent colleges. The price begins at around twenty dollars for a diploma from "Smoot State University". The prices increase rapidly for a degree from the "University of Pudue". As there is no Smoot State and the real school in Indiana is properly called Pudue University, the prices seem rather high for one sheet of paper.

阅读理解What made Joan Ryan decide to be a sports writer? "Ten years ago, I was editing news stories at the Orlando Sentinel in Florida--my first job out of college. I didn''t know any female sports writers. But I wanted to be one. First of all, the best writing in the paper was sports." "Furthermore, I had the background. I grew up in an athletic family: Three boys and three girls and a coach for a dad. Soon after describing her ambition to a co-worker, the editor of her paper reassigned Joan to the sports department. Today, Joan is the sports columnist for the San Francisco Examiner in California. When she landed her job eight years ago, she was the only woman sports writer on any major American newspaper. (She is now one in about six.) Was it tough to pioneer as a female sports writer? You bet ! Take for example, the first time Joan tried to get an interview in the men'' s locker room. "It was the U. S. Football League. I wanted to interview one of the players, Joe Cribbs, because he had just broken a finger. As soon as I stepped into the locker room--where all sports writers interview athletes--the room went crazy. Guys started yelling at me. It was really terrible. Suddenly I felt something move up my leg. It was the handle of the razor (剃刀) that someone used to cut the tape. I yelled and walked out." Joan ended up interviewing Cribbs--outside the locker room. "In retrospect (回顾), I feel this was a defining moment for me as a journalist. I went back and wrote my story and made my headline. Now I know for sure that nothing can interfere with getting the story." If you want to be a sports writer, Joan suggests that you read "the best fiction writers" and learn how to write well. Her other suggestions: "Don''t let anyone keep you from doing what you want to do. Just pretend you have courage."

阅读理解With a mixed feeling of pride and discontent, Prof. Mitchell sat on the front lawn of Princeton High School, watching the Class of 2004 (47) . Her pride was for the seniors'' average SAT score of 1237, third-highest in the state, and their admission to famous universities like Harvard, Yale and Duke. As president of the high school alumni(校友) association, Ms. Mitchell deserved to (48) the tradition of public-education excellence. Though, she felt quite (49) about Blake, her own son. He was receiving his diploma on this June afternoon only after years of struggle. More often than not, the science teacher said he was merely (50) of C''s. Even at that, Ms. Mitchell realized, Blake had done (51) better than several friends who were not (52) at the graduation ceremony. They were headed instead for crash courses(补习班). "I said to myself: ''Oh, no. Please, no, ''" Ms. Mitchell recalled. "I was so hurt. These were (53) kids. This shouldn''t have been happening." It did not escape Ms. Mitchell''s notice that her son and most of those less (54) classmates were black. They were the (55) of an accomplished school district''s dirty little secret, a racial achievement gap that has been (56) and left uncorrected for decades. Now that pattern may have to change under the pressure of the federal No Child Left Behind law. WORD BANK [A] absent [F] graduate [K] bright [B] pleased [G] capable [L] enjoy [C] dissatisfied [H] successful [M] slightly [D] weakness [I] hardly [N] recognized [E] finish [J] evidence [O] present

阅读理解With 950 million people, India ranks second to China among the most populous(人口多的) countries. But since China launched a family planning program in 1971, India has been (47) the gap. Indians have reduced their birth rate but not nearly as much as the Chinese have. If current growth rates continue, India''s population Will (48) China''s around the year 2028 at about 1.7 billion. Should that happen, it won''t be the (49) of the enlightened women of Kerala, a state in southern India. While India as a whole adds almost 20 million people a year, Kerala''s population is virtually (50) . The reason is no (51) : nearly two thirds of Kerala women practice birth control, compared with about 40% in the entire nation. The difference lies in the emphasis put on health programs, including birth control, by the state authorities. And an educational tradition and matrilineal (母系的) customs in parts of Kerala help girls and boys get (52) good schooling. While one in three Indian women is (53) , 90% of those in Kerala can read and write. Higher literacy rates (54) family planning. "Unlike our parents, we know that we can do more for our children if we have fewer of them," says Leila Cherian, 33, who lives in the village of Kudamaloor. She has limited herself to three children—one below the (55) average of four. That kind of restraint (抑制；克制) will keep Kerala from putting added (56) on world food supplies. WORD BANK [A] stable [F] flexible [K] foster [B] widening [G] closing [L] mystery [C] educated [H] exceed [M] national [D] pressure [I] equally [N] advocate [E] fault [J] general [O] officially

阅读理解Is there enough oil beneath the Arctic National Wildlife Refuge (保护区) (ANWR)to help secure America''s energy future? President Bush certainly thinks so. He has argued that tapping ANWR''s oil would help ease California''s electricity crisis and provide a major boost to the country''s energy independence. But no one knows for sure how much crude oil lies buried beneath the frozen earth, with the last government survey, conducted in 1998, projecting output anywhere from 3 billion to 16 billion barrels. The oil industry goes with the high end of the range, which could equal as much as 10% of U.S. consumption for as long as six years. By pumping more than 1 million barrels a day from the reserve for the next two to three decades, lobbyists claim, the nation could cut back on imports equivalent to all shipments to the U.S. from Saudi Arabia. Sounds good. An oil boom would also mean a multibillion-dollar windfall (意外之财) in tax revenues, royalties (开采权使用费) and leasing fees for Alaska and the Federal Government. Best of all, advocates of drilling say, damage to the environment would be insignificant. "We''ve never had a documented case of an oil rig chasing deer out onto the pack ice," says Alaska State Representative Scott Ogan. Not so fast, say environmentalists. Sticking to the low end of government estimates, the National Resources Defense Council says there may be no more than 3.2 billion barrels of economically recoverable oil in the coastal plain of ANWR, a drop in the bucket that would do virtually nothing to ease America''s energy problems. And consumers would wait up to a decade to gain any benefits, because drilling could begin only after much bargaining over leases, environmental permits and regulatory review. As for ANWR''s impact on the California power crisis, environmentalists point out that oil is responsible for only 1% of the Golden State''s electricity output—and just 3% of the nation''s.

阅读理解Passage one Aging happens to all of us ,and is generylly thought of as a natural part of life

阅读理解To call something "marginal" means it is not very good. Farmers have their own way to (47) marginal land: It is the last to be planted under good conditions, and has the (48) to be avoided under poor conditions. Low (49) soil is not the only reason land could be considered marginal. It might be in an area where rainfall is (50) or where a hillside might rise too steeply (陡峭地). There are uses for marginal land, however. Most often it is used as grassland. Grasses provide excellent (51) for grazing (吃草) animals like cattle, sheep and goats. Grass seed can be bought from a foreign supplier or (52) grasses can be used. However, using marginal land for grazing is not a simple issue. There is a (53) of overgrazing. Cattle can damage the crops by eating down to the roots. Also, the weight of the animals crushes the soil and can make it too hard for growing. A(n) (54) way to reduce the harm is to move animals from one field to another. This method is known as rotational grazing (循环放牧) which is extremely important for marginal land. Another use for marginal land is for tree crops. Studies have (55) that the white pine and loblolly pine (火炬松) are two kinds of trees that grow well on such land. They grow fast and provide good quality wood. Another tree is the poplar (白杨), found in many parts of the world. Failure to take the care needed to protect marginal lands can make a bad situation worse. But good planning can (56) a marginal resource into a highly productive one. WORD BANK A) feed I) discouraging B) priority J) quality C) transplant K) native D) effective L) revealed E) limited M) prejudice F) define N) hazard G) adequate O) recovered H) transform

阅读理解"Tear''em apart! ""Kill the fool! ""Murder the referee (裁判) !" These are common remarks one may hear at various sporting events. At the time they are made, they may seem innocent enough. But let''s not kid ourselves. They have been known to influence behavior in such a way as to lead to real bloodshed. Volumes have been written about the way words affect us. It has been shown that words having certain connotations (含义) may cause us to react in ways quite foreign to what we consider to be our usual humanistic behavior. I see the term "opponent" as one of those words. Perhaps the time has come to delete it from sports terms. The dictionary meaning of the term "opponent" is "adversary"; "enemy"; "one who opposes your interests." Thus, when a player meets an opponent, he or she may tend to treat that opponent as an enemy. At such times, winning may, dominate one''s intellect, and every action, no matter how gross, may be considered justifiable. I recall an incident in a handball game when a referee refused a player''s request for a time out for a glove change because he did not consider them wet enough. The player proceeded to rub his gloves across his wet T-shirt and then exclaimed, "Are they wet enough now?" In the heat of battle, players have been observed to throw themselves across the court without considering the consequences that such a move might have on anyone in their way. I have also witnessed a player reacting to his opponent''s intentional and illegal blocking by deliberately hitting him with the ball as hard as he could during the course of play. Off the court, they are good friends. Does that make any sense? It certainly gives proof of a court attitude which departs from normal behavior. Therefore, I believe it is time we elevated (提升) the game to the level where it belongs, thereby setting an example to the rest of the sporting world. Replacing the term "opponent" with "associate" could be an ideal way to start. The dictionary meaning of the term "associate" is "colleague"; "friend"; "companion." Reflect a moment! You may soon see and possibly feel the difference in your reaction to the term "associate" rather than "opponent."

阅读理解Women''s mind work differently from men''s at least, that is what most men are convinced of. Psychologists view the subject either as a matter of frustration or a joke. Now the biologists have moved into this minefield, and some of them have found that there are real social differences between the brains of men and women. But being different, they point out hurriedly, is not the same as being better or worse. There is, however, a definite structural variation between the male and female brain. The difference is in a part of the brain that is used in the most complex intellectual processes — the link between the two halves of the brain. The two halves are linked by a trunkline of between 200 and 300 million nerves, the corpus callosum(胼胝质). Scientists have found quite recently that the corpus callosum in women is always larger and probably richer in nerve fibres(纤维) than it in men. This is the first time that a structural difference has been found between the brains of women and men and it must have some significance. The question is "what?", and if this difference exists, are mere others? Research shows that present-day women think differently and behave differently from men. Are some of these differences biological and inborn, a result of evolution? We tend to think that is the influence of society that produces these differences. But could we be wrong? Research showed that these two halves of the brain had different functions, and that the corpus callosum enabled them to work together. For most people, the left half is used for word-handling, analytical and logical activities; the right half works on pictures, patterns and forms. We need both halves working together. And the better the connections, the more harmoniously the two halves work. And, according to research findings, women have the better connections. But it isn''t all that easy to explain the actual differences between skills of men and women on this basis. In schools throughout the world girls tend to be better than boys at "language subjects" and boys better at maths and physics. If these differences correspond with the differences in the hemispheric(半球的) trunkline, there is an unalterable distinction between the sexes. We shan''t know for a while, partly because we don''t know of any precise relationship between abilities in school subjects and the functioning of the two halves of the brain, and we cannot understand how the two halves interact via the corpus callosum. But this striking difference must have some effect and, because the difference is in the parts of the brain involved in intellect, we should be looking for differences in intellectual processing.

阅读理解The country of Croatia may have given birth to the necktie. Sometime during the 1630s or 1640s, Croatian mercenaries(雇佣军) involved in the Thirty Years'' War visited King Louis XIV of France. The king was very (47)______ by the soldiers'' traditional uniforms, which (48)______ soft scarves tied around their necks. By 1650, Louis and his court were wearing Croatian neck scarves instead of the full lace ruffs that had (49)______ been fashionable. Some sources suggest the Croatians weren''t the first to wear neckties. One of the oldest examples of a necktie is found on the life-size terracotta soldiers buried with Chinese emperor Shih Huang Ti in 210 B.C.. Each solider wears a carefully (50)______ silk cloth around its neck. However, these images are unique, and there is no (51)______ that Chinese men commonly wore neckties. It seems clear that King Louis XTV (52)______ the necktie. Exiled King Charles II of England brought the French cravat with him when he returned to his throne. Englishmen soon began sporting stylish neck scarves and tied them in as many as 100 different knots. In the early 1800s, English dandy George Bryan epitomized(成为缩影) high fashion and reportedly changed his crisp, white linen cravat three times a day. Styles of cravats changed and (53)______ over the years. The bow tie developed in the 1840s, and from the 1860s to the 1880s, cravats became narrower like the necktie we know today. In the 1890s, the four-in-hand knot (named for its resemblance to the knot used by a coach driver to control the horses'' reins) was (54)______ This continues to be one of the most popular knots. As for why men wear ties, this can only be explained as a whim of (55)______ . In King Louis XTV''s day, men wore elaborate outfits of brocade and lace. As the centuries wore on, the necktie has become the only remnant of those times. Today''s ties aren''t quite so fancy, but they can still (56)______ a splash of color and style to men''s dress. Word Bank A) fashion I) evidence B) popularized J) casually C) introduced K) add D) breed L) burden E) evolved M) featured F) impressed N) contributed G) boomed O) wrapped H) previously

阅读理解Technology to understand and analyze CVs just as a human would be launched in Europe by recruitment software innovator People Genie. The patented technology has been developed to create ''Smart Genie'', which will be fully integrated within the People Genie family of plug-in facilities. Smart Genie can analyze a job specification and by using predictive modeling it can rank CVs in order of their suitability based on over 40 analytical techniques. Additional features also include the ability to match any number of CVs with an ideal job role. Marc Hendrickse, Managing Director of People Genie said: "Smart Genie is a real breakthrough for the recruitment industry." There are some basic programs to read CVs, but by only searching against key words they can easily overlook the best candidates. This cutting edge technology uses artificial intelligence to understand each CV to the extent that it can spot the difference between a skill studied in a course and hands-on experience. "Traditional reading software does not eradicate the need for recruiters to sort through CVs, although they may have been able to eliminate up to half of a batch of 100 CVs by searching for a specific job title. Smart Genie will pioneer the way forward by enabling recruiters to spend more time with a true shortlist of candidates and less time processing irrelevant CVs." To link in with the other People Genie applications, Smart Genie has also been developed to assist with creating job adverts by suggesting all relevant skills for a role. It does this not only by utilizing its extensive built-in information library, but also by learning from every CV it reads. The program continuously improves by storing information gathered from CVs collected from all worldwide users enabling it to recognize the most relevant skills required to help attract quality candidates. Smart Genie will completely eliminate the need for recruiters to maintain an up-to-date skills library as it can easily be integrated with an existing database and then continuously up-dates and stores new information. Smart Genie will also help specialist recruiters to diversify by suggesting skills for job adverts and searching CVs in a whole range of industries, offering a powerful advantage over competitors.

阅读理解Lacking a cure for AIDS, society must offer education, not only by public pronouncement but in classrooms. Those with AIDS or those at high risk of AIDS suffer prejudice, they are feared by some people who find living itself unsafe, while others conduct themselves with a "bravado (冒险心理)" that could be fatal. AIDS has afflicted a society already short on humanism, open-handedness and optimism. Attempts to strike it out with the offending microbe are not abetted (教唆) by pre-existing social ills. Such concerns impelled me to offer the first university-level undergraduate AIDS course, with its two important aims: To address the fact that AIDS is caused by a virus, not by moral failure or societal collapse. The proper response to AIDS is compassion coupled with an understanding of the disease itself. We wanted to foster(help the growth of) the idea of a humane society. To describe how AIDS tests the institutions upon which our society rests. The economy, the political system, science, the legal Establishment, the media and our moral ethical-philosophical attitudes must respond to the disease. Those responses, whispered, or shrieked, easily accepted or highly controversial, must be put in order if the nation is to manage AIDS. Scholars have suggested that how a society deals with the threat of AIDS describes the extent to which that society has the right to call itself civilized. AIDS, then, is woven into the tapestry (挂毯) of modem society; in the course of explaining that tapestry, a teacher realizes that AIDS may bring about changes of historic proportions. Democracy obliges its educational system to prepare students to become informed citizens, to join their voices to the public debate inspired by AIDS. Who shall direct just what resources of manpower and money to the problem of AIDS? Even more basic, who shall formulate a national policy on AIDS? The educational challenge, then, is to enlighten(启发) the individual and the societal, or public, responses to AIDS.

阅读理解THE HYDROGEN ECONOMY It seems like every day there is a new announcement in the news about automobiles powered by fuel cells. The promises are great, since fuel cells have the potential to very quickly double the efficiency of cars while significantly reducing air pollution. At the same time, there have been news stories for decades about the problems associated With petroleum. Everything from oil spills to ozone(臭氧) alerts to global warming gets blamed on our dependence on fossil(化石) fuels. These two forces are leading the world toward what is broadly known as the hydrogen economy. If the predictions are true, over the next several decades we will all begin to see an amazing shift away from the fossil fuel economy we have today toward a much cleaner hydrogen future. Problems with the fossil fuel economy While fossil fuels have played an important role in getting society to the point it is at today, there are four big problems that fossil fuels create: Air pollution--When cars burn gasoline, the internal combustion engine also produces: Carbon monoxide, a poisonous gas Nitrogen oxides, the main source of urban smog Unburned hydrocarbons, the main source of urban ozone Environmental pollution--The process of transporting and storing oil has a big impact on the environment whenever something goes wrong. An oil spill, pipeline explosion or well fire can create a huge mess. Global warming—The carbon dioxide coming out of every car''s tailpipe is a greenhouse gas that is slowly raising the temperature of the planet. The ultimate effects are unknown, but it is a strong possibility that, eventually, there will be dramatic climate changes that affect everyone on the planet. Dependence--The United States, and most other Countries, cannot produce enough oil to meet demand, so they import it from oil-rich countries. That creates an economic dependence. When Middle East oil producers decide to raise the price of oil, the rest of the world has little choice but to pay the higher price. Advantages of the hydrogen economy The hydrogen economy promises to eliminate all of the problems that the fossil fuel economy creates. Therefore, the advantages of the hydrogen economy include: The elimination of pollution caused by fossil fuels-When hydrogen is used in a fuel cell to create power, it is a completely clean technology. The only byproduct is water. There are also no environmental dangers like oil spills to worry about with hydrogen. The elimination of greenhouse gases--If the hydrogen comes from the electrolysis of water, then hydrogen adds no greenhouse gases to the environment. There is a perfect cycle--electrolysis produces hydrogen from water, and the hydrogen recombines with oxygen to create water and power in a fuel cell. The elimination of economic dependence--The elimination of oil means no dependence on the Middle East and its oil reserves. Distributed production--Hydrogen can be produced anywhere that you have electricity and water. People can even produce it in their homes with relatively simple technology. The problems with the fossil fuel economy are so great, and the environmental advantages of the hydrogen economy so significant, that the push toward the hydrogen economy is very strong. Technological Hurdles(障碍) The big question with the hydrogen economy is, "Where does the hydrogen come from?" After that comes the question of transporting, distributing and storing hydrogen. Hydrogen tends to be large and tricky in its natural gaseous form. Once both of these questions are answered in an economical way, the hydrogen economy will be in place. Where does the hydrogen come from? There are two possible sources for the hydrogen: Electrolysis of water--Using electricity, it is easy to split water molecules to create pure hydrogen and oxygen. One big advantage of this process is that you can do it anywhere. For example, you could have a box in your garage producing hydrogen from tap water, and you could fuel your car with that hydrogen. Reforming fossil fuels--Oil and natural, gas contain hydrocarbons--molecules consisting of hydrogen and carbon. Using a device called a fuel processor or a reformer, you can split the hydrogen off the carbon in a hydrocarbon relatively easily and then use the hydrogen. You discard the leftover carbon to the atmosphere as carbon dioxide. The second option is, of course, slightly perverse(不正当的). You are using fossil fuel as the source of hydrogen for the hydrogen economy. This approach reduces air pollution, but it doesn''t solve either the greenhouse gas problem or the dependence problem. However, it may be a good temporary step to take during the transition(转变) to the hydrogen economy. The interesting thing about the first option is that it is the core of the real hydrogen economy. To have a pure hydrogen economy, the hydrogen must be derived from renewable sources rather than fossil fuels so that we stop releasing carbon into the atmosphere. Having enough electricity to separate hydrogen from water, and generating that electricity without using fossil fuels, will be the biggest change that we see in creating the hydrogen economy. Where will the electricity for the electrolysis of water come from? Currently, about 68 percent of the electricity produced in the United States comes from coal or natural gas. All of that generating capacity will have to he replaced by renewable sources in the hydrogen economy. Right now there are several different ways to create electricity that do not use fossil fuels: Nuclear power Hydroelectric dams Solar cells Wind turbines Geothermal power Wave and tidal power Co-generation How do you store and transport the hydrogen? Hydrogen is a large gas of its kind, and it is not nearly as easy to work with as gasoline. Compressing the gas requires energy, and compressed hydrogen contains far less energy than the same volume of gasoline. However, solutions to the hydrogen storage problem are surfacing. For example, hydrogen can be stored in a solid form in a chemical called sodium borohydride. Once the storage problem is solved and standardized, then a network of hydrogen stations and the transportation infrastructure will have to develop around it. The main barrier to this might be the technological sorting-out process. Stations will not develop quickly until there is a storage technology that clearly dominates the marketplace. For instance, if all hydrogen-powered cars from all manufacturers used sodium borohydride, then a station network could develop quickly; that sort of standardization is unlikely to happen rapidly, if history is any guide. Prospects for the future You will hear more and more about the hydrogen economy in the news in the Coming months, because the drumbeat is growing louder. The environmental problems of the fossil fuel economy are combining with breakthroughs(突破) in fuel-cell technology, and the pairing will allow us to take the first steps, The most obvious step we will see is the marketing of fuel-cell-powered vehicles. Although they will be powered initially by gasoline and reformers, fuel cells represent two major improvements over the internal combustion engine: They are about twice as efficient. They can significantly reduce air pollution in cities.