was designed many years ago，with a goal in mind：transmitting the human voice in a more-or-less recognizable form．A．DWDMB．PSTNC．internetD．WLAN
was designed many years ago，with a goal in mind：transmitting the human voice in a more-or-less recognizable form．
A．DWDM
B．PSTN
C．internet
D．WLAN
相关考题：
About 300 years ago, many people __________.A． wanted to leave LondonB． had big houses in LondonC． became policemenD． came to live in London
A project can best be defined as:A.Series of non-related activities designed to accomplish single and multiple objectives.B.Coordinated effort of related activities designed to accomplish a goal without a well-established end point.C.Cradle-to-grave activities which must be accomplished in less than one year and consumes human and non-human resources.D.Any undertaking with a definable time frame, well-defined objectives, and consumes both human and non-human resources with certain constraints.E.All of the above.
People tend to talk about presents in a fairly loving way. A woman whose mother had died years ago described the many gifts around her house.These were gifts that her mother had given her over the years:“I appreciate these, and they mean something to me,”the woman said,“because I remember the occasions they were given on, and that they were from my mother, and the relationship we’ve had.”The gifts remain and keep the relationship alive in mind. This woman felt the same way about the gifts she gave to others. She hoped that the recipients would look at here gifts in years to come and
32 jack descried his father, who _____a brave boy many years ago, as a strong-wiled manA. would beB. would have beenC. must beD. must have been
We may conclude from the text that .［A］ human cloning will not succeed unless the technique is more efficient［B］ scientists are optimistic about cloning technique［C］ many people are against the idea of human cloning［D］ cloned animals are more favored by owners even if they are weaker
I wonder how many years ago _______.A.did you father retireB.your father retiredC.has your father retiredD.your father has retired
完形填空Many of the world’s pollution problems have been caused by the crowding of large groups of people into cities.Satisfying the 21 of the people leads to further polluting by industry.If the rapid increase in human population 22 at the present rate (比率), there may be much greater harm.Some scientists speak of the 23 in number of people as “Population Pollution”.About 2000 years ago, the world 24 was probably about 250 million.It reached a billion in 1850.By 1930 the population was two billion.It is 25 three and a half billion.It is expected to double by the year 2000.If the population continues to grow at the same 26 , there would be 25 billion people in the world a hundred years from now.Man has been using the earth’s 27 more and more rapidly over the years.Some of them are almost gone.Now many people believe that man’s greatest 28 is how to control the growth of this population.The materials in the world will not support the human population in time to come if the present rate of increase continues.29 there is over crowding in the cities and hunger in some countries.Can man’s rate of increase continue?Many people believe that human survival (幸存者) in the future 30 on the answer to the question.21.A.needsB.suppliesC.serviceD.supports22.A.stopsB.continuesC.slows downD.adds to23.A.increaseB.reduceC.countryD.improvement24.A.peopleB.situationC.populationD.land25.A.nowB.in the pastC.in the futureD.then26.A.placeB.timeC.rateD.result27.A coalB.oilC.minesD.resources28.A.problemB.powerC.planD.idea29.A.AlreadyB.YetC.StillD.Often30.A.feedsB.livesC.keepsD.depends
I started my teaching career at the school. That was more than twenty years ago, and I _____ there ever since.A. wasB. had beenC. will beD. have been
Compared with parents of 30 years ago, today's parents ( )．A． go to clubs more often with their childrenB． are much stricter with their childrenC． care less about．their children's lifeD． give their children more freedom
Edison invented the light bulb many years ago（改为被动语态）The light bulb__________ __________by Edison many years ago．
共用题干Older Volcanic EruptionsVolcanoes were more destructive in ancient history,not because they were bigger,but because the carbon dioxide they released wiped out life with greater ease.Paul Wignall from the University of Leeds was investigating the link between volcanic eruptions and mass extinctions.Not all volcanic eruptions killed off large numbers of animals,but all the mass extinctions over the past 300 million years coincided with huge formations of volcanic rock.To his surprise,the older the massive.volcanic eruptions were,the more damage they seemed to do.He calculated the"killing efficiency" for these volcanoes by comparing the proportion of life they killed off with the volume of lava（熔岩）that they produced.He found that size for size,older eruptions were at least 10 times as effective at wiping out life as their more recent rivals.The Permian（二叠纪）extinction,for example,which happened 250 million years ago,is marked by floods of volcanic rock in Siberia that cover an area roughly the size of western Europe.Those volcanoes are thought to have pumped out about 1 0 gigatonnes（十亿吨）of carbon as carbon dioxide.The global warming that followed wiped out 80 percent of all marine genera（种类）at the time,and it took 5 million years for the planet to recover.Yet 60 million years ago,there was another huge amount of volcanic activity and global warming but no mass extinction.Some animals did disappear but things returned to normal within ten thousands of years."The most recent ones hardly have an effect at all,"Wignall says.He ignored the extinction which wiped out the dinosaurs 65 million years ago,because many scientists believe it was primarily caused by the impact of an asteroid（小行星）.He thinks that older volcanoes had more killing power because more recent life forms were better adapted to dealing with increased levels of CO2.Vincent Courtillot,director of the Paris Geophysical InstitUte in France,says that Wignall's idea is provoca- tive.But he says it is incredibly hard to do these sorts of calculations.He points out that the killing power of volcanic eruptions depends on how long they lasted.And it is impossible to tell whether the huge blasts lasted for thousands or millions of years.He also adds that it is difficult to estimate how much lava prehistoric volcanoes produced,and that lava volume may not necessarily correspond to carbon dioxide emissions.Permian extinction occurred______.A:300 million years ago B:250 million years agoC:60 million years ago D:65 million years ago
Compared with parents of 30 years ago，today’s parents__________．A.go to clubs more often with their childrenB.are much stricter with their childrenC.care less about their children’s lifeD.give their children more freedom
Years ago,a cigarette commercial asked if you were smoking more,but enjoying it less．That describes the way many of us live today．We are doing more,but enjoying it less．And when that doesn't work,we get the problem．In our extremely hurried search for satisfaction,we try stuffing still more into our days,never realizing that we are taking the wrong approach.The truth is simple;so simple it is hard to believe．Satisfaction lies with less,not with more．Yet,we pursue the myth that this thing,or that activity,will somehow provide the satisfaction we so desperately seek.Arthur Lindman,in his very effective book,"The Harried Leisure Class,"described the uselessness of pursuing more．His research focused on what people did with their leisure time．He found that as income rose,people bought more things to occupy their leisure time．But,ironically,the more things they bought,the less they valued any one of them．Carried to an extreme,he predicted massive boredom in the midst of tremendous variety．That was more than twenty years ago,and his prediction seems more accurate every year.Lindman of course,is not the first to discover this．The writer of Ecclesiastes expressed the same thought thousands of years ago．It is better,he wrote,to have less,but enjoy it more.If you would like to enjoy life more,I challenge you to experiment with me．How could you simplify your life?What could you drop?What could you do without?What could you stop pursuing?What few things could you concentrate on?The more I learn,the more I realize that fullness of life does not depend on things．The more I give up,the more I seem to gain．But words will never convince you．You must try it for yourself．Lindman wrote his book__.A.ten years agoB.twenty years agoC.more than twenty years agoD.thousands of years ago
共用题干Older Volcanic EruptionsVolcanoes were more destructive in ancient history,not because they were bigger,but because the carbon dioxide they released wiped out life with greater ease.Paul Wignall from the University of Leeds was investigating the link between volcanic eruptions and mass extinctions.Not all volcanic eruptions killed off large numbers of animals,but all the mass extinctions over the past 300 million years coincided with huge formations of volcanic rock.To his surprise,the older the massive volcanic eruptions were,the more damage they seemed to do.He calculated the"killing efficiency" for these volcanoes by comparing the proportion of life they killed off with the volume of lava（熔岩）that they produced.He found that size for size,older eruptions were at least 10 times as effective at wiping out life as their more recent rivals.The Permian（二叠纪）extinction,for example,which happened 250 million years ago,is marked by floods of volcanic rock in Siberia that cover an area roughly the size of western Europe.Those volcanoes are thought to have pumped out about 10 gigatonnes of carbon as carbon dioxide.The global warming that followed wiped out 80 percent of all marine genera（种类）at the time,and it took 5 million years for the planet to recover.Yet 60 million years ago,there was another huge amount of volcanic activity and global warming but no mass extinction.Some animals did disappear but things returned to normal within ten thousand of years."The most recent ones hardlyhave an effect at all,"Wignall says.He ignored the extinction which wiped out the dinosaurs 65 million years ago,because many scientists believe it was primarily caused by the impact of an asteroid（小行星）.He thinks that older volcanoes had more killing power because more recent life forms were better adapted to dealing with increased levels of CO2．Vincent Courtill.ot,director of the Paris Geophysical Institute in France,says that Wignall's idea is provocative.But he says it is incredibly hard to do these sorts of calculations.He points out that the killing power of volcanic eruptions depends on how long they lasted.And it is impossible to tell whether the huge blasts lasted for tliousands or millions of years.He also adds that it is difficult to estimate how much lava prehistoric volcanoes produced,and that lava volume may not necessarily correspond to carbon dioxide emissions。When did dinosaurs become extinct?A:300 million years ago.B:250 milliOn years ago.C:60 million years ago.D:65 million years ago.
Our factory is much more productive now. This year’s production is five times as much （） it was ten years ago.AwhatBasCthatDthan
Electricity （） by the Greeks a good many years ago.Awas first foundBwas first discoveredChas first been discoveredDwas seen first
What two descriptions best define DWDM？ （）A、 a WDM system that is compatible with EDFA technologyB、 an optical technology for transmitting up to 16 channels over multiple fiber strandsC、 an optical technology for transmitting up to 32 channels over multiple fiber strandsD、 a technology for transmitting multiple optical signals using less sophisticated transceiver designthen CWDME、 a technology for transmitting more closely packed optical signals using more sophisticatedtransceiver designs than CWDM
How many years of experience do you have using any version of Windows Server? （）A、I have not done this yet.B、Less than 6 monthsC、More than 6 months but less than 1 yearD、1-2 yearsE、2-3 yearsF、More than 3 years
How many years of experience do you have with deploying and maintaining a virtualization infrastructure using any desktop or server virtualization technologies?（）A、I have not done this yet.B、Less than 6 monthsC、More than 6 months but less than 1 yearD、1 - 2 yearsE、2 - 3 yearsF、More than 3 years
单选题I wonder how many years ago _____.Adid your father retireByour father retiredChas your father retiredDyour father has retired
单选题The author of Passage 1 states that the human body is more like a garbage dump than a watch (lines 8－9) to emphasize that ______.Athe parts of the human body don't always work together seamlessly to keep us alive and functioningBthe human body cannot be counted on to work flawlessly, while watches rarely failCscientists can never tell ahead of time which experiments will work and which will notDthe human body exists in its present state due to a long evolutionary process that began more than 500 million years agoEthe human body contains many useless renmants left over from the evolutionary process
单选题There would be many more organ donors if ______.Alaws are designed to encourage organ recyclingBonly a few people become organ donorsCdoctors are more willing to ask for donationsDtransplant surgery is more successful
单选题More than two hundred years ago the United States _____ from the British Empire and became an independent country.Agot offBpulled downCbroke awayDdropped off
多选题What two descriptions best define DWDM？ （）Aa WDM system that is compatible with EDFA technologyBan optical technology for transmitting up to 16 channels over multiple fiber strandsCan optical technology for transmitting up to 32 channels over multiple fiber strandsDa technology for transmitting multiple optical signals using less sophisticated transceiver designthen CWDMEa technology for transmitting more closely packed optical signals using more sophisticatedtransceiver designs than CWDM
单选题Electricity （） by the Greeks a good many years ago.Awas first foundBwas first discoveredChas first been discoveredDwas seen first
单选题Our factory is much more productive now. This year’s production is five times as much （） it was ten years ago.AwhatBasCthatDthan
单选题For many years marine centrifuges were designed for （） operation, that is the machines were run for a period during which solids accumulated in the bowlThe machine was stopped when the accumulated solids began to impair its performance.ApurifyingBbatchClong periodDtemporary