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A、源IP地址
B、头部校验和
C、标志
D、总长度
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正确答案:

A

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Wecanbeginourdiscussionof“populationasglobalissue”withwhatmostpersonsmeanwhentheydiscuss“thepopulationproblem”:toomanypeopleonearthandatoorapidincreaseinthenumberaddedeachyear.Thefactsarenotindispute,Itwasquiterighttoemploytheanalogythatlikeneddemographicgrowthto“along,thinpowderfusethatburnssteadilyandhaltinglyuntilitfinallyreachesthechargeandexplodes.”

Tounderstandthecurrentsituation,whichischaracterizedbyrapidincreasesinpopulation,itisnecessarytounderstandthehistoryofpopulationtrends.Rapidgrowthisacomparativelyrecentphenomenon.Lookingbackatthe8,000yearsofdemographichistory,wefindthatpopulationshavebeenvirtuallystableorgrowingveryslightlyformostofhumanhistory.Formostofourancestors,lifewashard,oftennasty,andveryshort.Therewashighfertilityinmostplaces,butthiswasusuallybalancedbyhighmortality.Formostofhumanhistory,itwasseldomthecasethatoneintenpersonswouldlivepastforty,whileinfancyandchildhoodwereespeciallyriskyperiods.Often,societieswereincleardangerofextinctionbecausedeathratescouldexceedtheirbirthrates.Thus,thepopulationproblemthroughoutmostofhistorywashowtopreventextinctionofthehumanrace.

Thispatternisimportanttonotice.Notonlydoesitputthecurrentproblemsofdemographicgrowthintoahistoricalperspective,butitsuggeststhatthecauseofrapidincreaseinpopulationinrecentyearsisnotasuddenenthusiasmformorechildren,butanimprovementintheconditionsthattraditionallyhavecausedhighmortality.

Demographichistorycanbedividedintotwomajorperiods:atimeoflong,slowgrowthwhichextendedfromabout8,000BC.tillapproximatelyAD.1650.Inthefirstperiodofsome9600years,thepopulationincreasedfromsome8millionto500millionin1650.Between1650andthepresent,thepopulationhasincreasedfrom500milliontomorethan4billion.Anditisestimatedthatbytheyear2000therewillbe6.2billionpeoplethroughouttheworld.Onewaytoappreciatethisdramaticdifferenceinsuchabstractnumbersistoreducethetimeframetosomethingthatismoremanageable.Between8000BCand1650,anaverageofonly50,000personswasbeingaddedannuallytotheworld’spopulationeachyear.Atpresent,thisnumberisaddedeverysixhours.Theincreaseisabout80,000,000personsannually.

1.Whichofthefollowingdemographicgrowthpatternismostsuitableforthelongthinpowderfuseanalogy?

A.Avirtuallystableorslightlydecreasingperiodandthenasuddenexplosionofpopulation.

B.Aslowgrowthforalongtimeandthenaperiodofrapid,dramaticincrease.

C.Toomanypeopleonearthandafewrapidincreaseinthenumberaddedeachyear.

D.Alongperiodwhendeathratesexceedsbirthratesandthenashortperiodwithhigherfertilityandlowermortality.

2.Duringthefirstperiodofdemographichistory,societieswereoftenindangerofextinctionbecause___.

A.onlyoneintenpersonscouldlivepast40.

B.therewashighermortalitythanfertilityinmostplaces.

C.itwastoodangeroustohavebabiesduetothepoorconditions.

D.ourancestorshadlittleenthusiasmformorechildren.

3.Whichstatementistrueaboutpopulationincrease?

A.Theremightbeanincreaseof2.2billionpersonsfromnowtotheyear2000.

B.About50,000babiesareborneverysixhoursatpresent.

C.Between8000BCandthepresent,thepopulationincreaseisabout80,000,000personseachyear.

D.Thepopulationincreasedfasterbetween8000BCand1650thanbetween1650andthepresent.

4.Theauthorofthepassageintendsto___.

A.warnpeopleagainstthepopulationexplosioninthenearfuture.

B.comparethedemographicgrowthpatterninthepastwiththatafter1650.

C.findoutthecauseforrapidincreaseinpopulationinrecentyears.

D.presentusaclearandcompletepictureofthedemographicgrowth.

5.Theword“demographic”inthefirstparagraphmeans___.

A.statisticsofhuman.

B.surroundingsstudy.

C.accumulationofhuman.

D.developmentofhuman.

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GriffithworkedforafirmthatspecializedineconomicdevelopmentinWashingtonD.C.becausesheneededmoneytopayforherdebt.

Inthelast12yearstotalemploymentintheUnitedStatesgrewfasterthanatanytimeinthepeacetimehistoryofanycountry–from82to110millionbetween1973and1985–thatis,byafullonethird.Theentiregrowth,however,wasinmanufacturing,andespeciallyinno–blue-collarjobs…

Thistrendisthesameinalldevelopedcountries,andis,indeed,evenmorepronouncedinJapan.Itisthereforehighlyprobablethatin25yearsdevelopedcountriessuchastheUnitedStatesandJapanwillemploynolargeraproportionofthelaborforceInmanufacturingthandevelopedcountriesnowemployinfarming–atmost,10percent.TodaytheUnitedStatesemploysaround18millionpeopleinblue-collarjobsinmanufacturingindustries.By2010,thenumberislikelytobenomorethan12million.Insomemajorindustriesthedropwillbeevensharper.Itisquiteunrealistic,forinstance,toexpectthattheAmericanautomobileindustrywillemploymorethanone–thirdofitspresentblue-collarforce25yearshence,eventhoughproductionmightbe50percenthigher.

Ifacompany,anindustryoracountrydoesnotinthenextquartercenturysharplyincreasemanufacturingproductionandatthesametimesharplyreducetheblue-collarworkforce,itcannothopetoremaincompetitive–oreventoremain“developed.”Theattempttopreservesuchblue–collarjobsisactuallyaprescriptionforunemployment…

ThisisnotaconclusionthatAmericanpoliticians,laborleadersorindeedthegeneralpubliccaneasilyunderstandoraccept.WhatconfusestheissueevenmoreitthattheUnitedStatesisexperiencingseveralseparateanddifferentshiftsinthemanufacturingeconomy.Oneistheaccelerationofthesubstitutionofknowledgeandcapitalformanuallabor.Wherewespokeofmechanizationafewdecadesago,wenowspeakof“robotization“or“automation.”Thisisactuallymoreachangeinterminologythanachangeinreality.WhenHenryFordintroducedtheassemblylinein1909,hecutthenumberofman–hoursrequiredtoproduceamotorcarbysome80percentintwoorthreeyears–farmorethananyoneexpectstoresultfromeventhemostcompleterobotization.Butthereisnodoubtthatwearefacinganew,sharpaccelerationinthereplacementofmanualworkersbymachines–thatis,bytheproductsofknowledge.

1.Accordingtotheauthor,theshrinkageinthemanufacturinglaborforcedemonstrates______.

A.thedegreetowhichacountry’sproductionisrobotized

B.areductioninacountry’smanufacturingindustries

C.aworseningrelationshipbetweenlaborandmanagement

D.thedifferencebetweenadevelopedcountryandadevelopingcountry

2.Accordingtotheauthor,incoming25years,adevelopedcountryorindustry,inordertremaincompetitive,oughtto______.

A.reducethepercentageoftheblue-collarworkforce

B.preserveblue–collarjobsforinternationalcompetition

C.acceleratemotor–canmanufacturinginHenryFord’sstyle

D.solvetheproblemofunemployment

3.Americanpoliticiansandlaborleaderstendtodislike_____.

A.confusioninmanufacturingeconomy

B.anincreaseinblue–collarworkforce

C.internalcompetitioninmanufacturingproduction

D.adropintheblue–collarjobopportunities

4.Theword“prescription”in“aprescriptionforunemployment”maybetheequivalentto______

A.somethingrecommendedasmedicaltreatment

B.awaysuggestedtoovercomesomedifficulty

C.somemeasurestakeninadvance

D.adevicetodire

5.Thispassagemayhavebeenexceptedfrom________

A.amagazineaboutcapitalinvestment

B.anarticleonautomation

C.amotor-carmagazine

D.anarticleonglobaleconomy

IfonlyI_____playtheguitaraswellasyou!

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