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.
DBCBD
暂无解析
Ifthedrugproveseffectiveinhumantrials,itcouldenhancetheeffectivenessofexistingAIDSdrugsin________.
Whichfactorpusheduphouseprices?
PartIVTranslation
Thecaptainrealizedthatthementriedtodeceivehimsohemadethemworkveryhardfortherestofthevoyage.(PassageOne)
ThediscoveryoftheAntarcticnotonlyprovedoneofthemostinterestingofallgeographicaladventures,butcreatedwhatmightbecalled“theheroicageofAntarcticexploration”.Bytheirtremendousheroism,mensuchasShakleton,Scott,andAmundsencausedanewcontinenttoemergefromtheshadows,andyetthatheroicage,littlemorethanacenturyold,isalreadypassing.Modernscienceandinventionsarerevolutionizingtheendurance,futurejourneysintotheseicywasteswillprobablydependonmotorvehiclesequippedwithcaterpillartractionratherthanonthedogsthatearlierdiscoverersfoundsoinvaluableandhardlycomparable.
FewrealizethatthisAntarcticcontinentisalmostequalinsizetoSouthAmerica,andenormousfieldofworkawaitsgeographersandprospectors.Thecoastsofthiscontinentremaintobeaccuratelycharted,andthemapingofthewholeoftheinteriorpresentsaformidabletasktothecartographerswhoundertakethework.Oncetheirlaborsarecompleted,itwillbepossibletoprospectthevastnaturalresourceswhichscientistsbelievewillfurnishoneofthelargesttreasurehoardsofmetalsandmineralstheworldhasyetknown,andalmostinexhaustiblesourcesofcopper,coal,uranium,andmanyotheroreswillbecomeavailabletoman.SuchdiscoverieswillusherinaneraofpracticalexploitationoftheAntarcticwastes.
Thepolardarknesswhichhidesthiscontinentforthesixwintermonthswillbedefeatedbyhugebatteriesoflight,andmakepossibletheestablishingofair-fieldsforthefutureinter-continentalairservicesbymakingtheseareasaslightasday.Presentflyingrouteswillbecompletelychanged,fortheAntarcticrefuelingbaseswillmakeflightsfromAustraliatoSouthAmericacomparativelyeasyoverthe5,000milesjourney.
Theclimateisnotlikelytoofferaninsuperableproblem,fortheexplorerAdmiralByrdhasshownthattheclimateispossibleevenformencompletelyuntrainedforexpeditionsintothosefrozenwastes.Someofhispartiesweremenwhohadneverseensnowbefore,andyetherecordsthattheysurvivedtherigorsoftheAntarcticclimatecomfortably,sothat,providedthattheappropriateinstallationsaremade,wemayassumethathumanbeingsfromallcountriescouldlivetheresafely.Byrdevenaffirmsthatitisprobablythemosthealthyclimateintheworld,fortheintensecoldofthousandsofyearshassterilizethiscontinent,andrendereditabsolutelygermfree,withtheconsequencesthatordinaryandextraordinarysicknessanddiseasesfromwhichmansuffersinotherzoneswithdifferentclimatesarehereutterlyunknown.Thereexistnoproblemsofconservationandpreservationoffoodsupplies,forthelatterkeepindefinitelywithoutanysignsofdeterioration;itmayevenbethatlatergenerationswillcometoregardtheAntarcticasthenaturalstorehouseforthewholeworld.
Plansarealreadyonfoottosetuppermanentbasesontheshoresofthiscontinent,andwhatsofewyearsagowasregardedasa“deadcontinent”nowpromisestobeamostactivecenterofhumanlifeandendeavor.
1.WhendidmanbegintoexploretheAntarctic?
A.About100yearsago.
B.Inthiscentury.
C.Atthebeginningofthe19thcentury.
D.In1798.
2.Whatmusttheexplorersbe,eventhoughtheyhavemodernequipmentandtechniques?
A.Braveandtough
B.Stubbornandarrogant.
C.Well-likedandhumorous.
D.Stoutandsmart.
3.Themosthealthyclimateintheworldis___.
A.inSouthAmerica.
B.intheArcticRegion.
C.intheAntarcticContinent.
D.intheAtlanticOcean.
4.WhatkindofmetalsandmineralscanwefindintheAntarctic?
A.Magnetite,coalandores.
B.Copper,coalanduranium.
C.Silver,naturalgasanduranium.
D.Aluminum,copperandnaturalgas.
5.Whatisplannedforthecontinent?
A.Buildingdamsalongthecoasts.
B.Settingupseveralsummerresortsalongthecoasts.
C.Mappingthecoastandwholeterritory.
D.Settinguppermanentbasesonthecoasts.
Urbancongestionwouldgreatlyberelievedifthe____chargedonpublictransportweremorereasonable.