Scatteredthroughtheseasoftheworldarebillionsoftonsofsmallplantsandanimalscalledplankton.Mostoftheseplantsandanimalsaretoosmallforthehumaneyetosee.Theydriftaboutlazilywiththecurrents,providingabasicfoodformanylargeranimals.Planktonhasbeendescribedastheequivalentofthegrassesthatgrowonthedrylandcontinents,andthecomparisonisanappropriateone.Inpotentialfoodvaluehowever,planktonfaroutweighsthatofthelandgrasses.Onescientisthasestimatedthatwhilegrassesoftheworldproduceabout49billiontonsofvaluablecarbohydrateseachyear.Thesea’splanktongeneratesmorethantwiceasmuch.

Despiteitsenormousfoodpotential,littleeffortwasmadeuntilrecentlytofarmplanktonaswefarmgrassesonland.Nowmarinescientistshaveatlastbeguntostudythispossibility,especiallyasthesea’sresourcesloomevenmoreimportantasameansoffeedinganexpandingworldpopulation.

Nooneyethasseriouslysuggestedthat“planktonburgers”maysoonbecomepopulararoundtheworld.Asapossiblefarmedsupplementaryfoodsource,however,planktonisgainingconsiderableinterestamongmarinescientists.

Onetypeofplanktonthatseemstohavegreatharvestpossibilitiesisatinyshrimplikecreaturecalledkrill.Growingtotwoorthreeincheslong,krillprovidethemajorfoodforthegiantbluewhale,thelargestanimalevertoinhabittheEarth.Realizingthatthiswhalemaygrow100feetandweigh150tonsatmaturity,itisnotsurprisingthateachonedevoursmorethanonetonofkrilldaily.

Krillswimaboutjustbelowthesurfaceinhugeschoolssometimesmileswide,mainlyinthecoldAntarctic.Becauseoftheirpinkcolor,theyoftenappearasasolidreddishmasswhenviewedfromashiporfromtheair.Krillareveryhighinfoodvalue.Apoundofthesecrustaceanscontainsabout460calories—aboutthesameasshrimporlobster,towhichtheyarerelated.

Ifthekrillcanfeedsuchhugecreaturesaswhales,manyscientistsreason,theymustcertainlybecontendersasnewfoodsourceforhumans.

1.Whichofthefollowingbestportraystheorganizationofthepassage?

A.Theauthorpresentstheadvantagesanddisadvantagesofplanktonasafoodsource.

B.Theauthorquotespublicopiniontosupporttheargumentforfarmingplankton.

C.Theauthorclassifiesthedifferentfoodsourcesaccordingtoamountofcarbohydrate.

D.Theauthormakesageneralstatementaboutplanktonasafoodsourceandthenmovestoaspecificexample.

2.Accordingtothepassage,whyisplanktonregardedtobemorevaluablethanlandgrasses?

A.Itiseasiertocultivate.

B.Itproducesmorecarbohydrates.

C.Itdoesnotrequiresoil.

D.Itismorepalatable.

3.Whydoestheauthormention“planktonburgers”?

A.Todescribetheappearanceofonetypeofplankton.

B.Toillustratehowmuchplanktonawhaleconsumes.

C.Tosuggestplanktonasapossiblefoodsources.

D.Tocomparethefoodvaluesofbeefandplankton.

4.Whatismentionedasoneconspicuousfeatureofkrill?

A.Theyarethesmallestmarineanimals.

B.Theyarepinkincolor.

C.Theyaresimilarinsizetolobsters.

D.Theyhavegrasslikebodies.

5.Theauthormentionsallofthefollowingasreasonswhyplanktoncouldbeconsideredahumanfoodsourceexceptthatitis___.

A.highinfoodvalue.

B.inabundantsupplyintheoceans.

C.anappropriatefoodforotheranimals.

D.freeofchemicalsandpollutants.

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.

Urbancongestionwouldgreatlyberelievedifthe____chargedonpublictransportweremorereasonable.

Bysaying"thegrowthoftheproportion...toyoungergenerations."(Line2,Para.5),AntheaTinkerreallymeansthat________.

Whatdoesthefutureholdfortheproblemofhousing?Agooddealdepends,ofcourse,onthemeaningof“future”.Ifoneisthinkingintermsofsciencefictionandthespaceage,itisatleastpossibletoassumethatmanwillhavesolvedsuchtrivialandearthlyproblemsashousing.Writersofsciencefiction,fromH.G.Wellsonwards,havehadlittletosayonthesubject.Theyhaveconveyedthesuggestionthatmenwillliveingreatcomfort,witheveryconceivableapparatustomakelifesmooth,healthyandeasy,ifnothappy.Buttheyhavenotsaidwhathishousewillbemadeof.Perhapssomenewbuildingmaterial,asyetunimagined,willhavebeendiscoveredorinventedatleast.Onemaybecertainthatbricksandmortar(泥灰，灰浆)willlonghavegoneoutoffashion.

Buttheproblemsofthenextgenerationortwocanmorereadilybeimagined.Scientistshavealreadypointedoutthatunlesssomethingisdoneeithertorestricttheworld’srapidgrowthinpopulationortodiscoveranddevelopnewsourcesoffood(orboth),millionsofpeoplewillbedyingofstarvationoratthebestsufferingfromunderfeedingbeforethiscenturyisout.Butnobodyhasyetworkedoutanyplanforhousingthesegrowingpopulations.Admittedlytheworstsituationswilloccurinthehottestpartsoftheworld,wherehousingcanbelightstructureorinbackwardareaswherestandardsaretraditionallylow.Buteventheminimumshelterrequiresmaterialsofsomekindandintheteeming,bulgingtownsthelow-standard“housing”offlattenedpetrolcansanddirtycanvasisfarmorewastefulofgroundspacethancanbetolerated.

Sincethewar,HongKonghassufferedthekindofcrisiswhichislikelytoariseinmanyotherplacesduringthenextgeneration.Literallymillionsofrefugeesarrivedtoswellthealreadygrowingpopulationandemergencystepshadtobetakenrapidlytopreventsqualor(肮脏)anddiseaseandthespreadcrime.Thecityistacklingthesituationenergeticallyandenormousblocksoftenements(贫民住宅)arerisingatanastonishingaped.ButHongKongisonlyonesmallpartofwhatwillcertainlybecomeavastproblemandnotmerelyahousingproblem,becausewhenpopulationgrowsatthisratethereareaccompanyingproblemsofeducation,transport,hospitalservices,drainage,watersupplyandsoon.NoteveryareamaygivethesameresourcesasHongKongtodrawuponandthesearchforquickerandcheapermethodsofconstructionmustnevercease.

1.Whatistheauthor’sopinionofhousingproblemsinthefirstparagraph?

A.Theymaybecompletelysolvedatsometimeinthefuture.

B.Theyareunimportantandeasilydealtwith.

C.Theywillnotbesolveduntilanewbuildingmaterialhasbeendiscovered.

D.Theyhavebeendealtwithinspecificdetailinbooksdescribingthefuture.

2.Thewriterissurethatinthedistantfuture___.

A.bricksandmortarwillbereplacedbysomeotherbuildingmaterial.

B.anewbuildingmaterialwillhavebeeninvented.

C.bricksandmortarwillnotbeusedbypeoplewhowanttheirhousetobefashionable.

D.anewwayofusingbricksandmortarwillhavebeendiscovered.

3.Thewriterbelievesthatthebiggestproblemlikelytoconfronttheworldbeforetheendofthecentury___.

A.isdifficulttoforesee.

B.willbehowtofeedtheevergrowingpopulation.

C.willbehowtoprovideenoughhousesinthehottestpartsoftheworld.

D.isthequestionoffindingenoughgroundspace.

4.Whenthewritersaysthattheworstsituationswilloccurinthehottestpartsoftheworldorinbackwardareas,heisreferringtothefactthatintheseparts___.

A.standardsofbuildingarelow.

B.onlyminimumshelterwillbepossible.

C.thereisnotenoughgroundspace.

D.thepopulationgrowthwillbethegreatest.

5.WhichofthefollowingsentencesbestsummarizesParagraph3?

A.HongKonghasfacedaseriouscrisiscausedbymillionsofrefugees.

B.HongKonghassuccessfullydealtwiththeemergencycausedbymillionsofrefugees.

C.HongKong’scrisiswasnotonlyamatterofhousingbutincludedanumberofotherproblemsofpopulationgrowth.

D.ManypartsoftheworldmayhavetofacethekindofproblemsencounteredbyHongKongandmayfinditmuchhardertodealwiththem.