距离英语四六级考试越来越近了，相信考生都打起精神准备进行最后的冲刺了。英语四级考试中阅读所占比重为百分之三十五，阅读的重要性不言而喻。
Itishardtotrackthebluewhale,theocean’slargestcreature,whichhasalmostbeenkilledoffbycommercialwhalingandisnowlistedasanendangeredspecies.Attachingradiodevicestoitisdifficult,andvisualsightingsaretoounreliabletogiverealinsightintoitsbehavior.
Sobiologistsweredelightedearlythisyearwhen,withthehelpoftheNavy,theywereabletotrackaparticularbluewhalefor43days,monitoringitssounds.ThiswaspossiblebecauseoftheNavy’sformerlytop-secretsystemofunderwaterlisteningdevicesspanningtheoceans.
TrackingwhalesisbutoneexampleofanexcitingnewworldjustopeningtocivilianscientistsafterthecoldwarastheNavystartstoshareandpartlyuncoveritsglobalnetworkofunderwaterlisteningsystembuiltoverthedecadestotracktheshipsofpotentialenemies.
Earthscientistsannouncedatanewsconferencerecentlythattheyhadusedthesystemforcloselymonitoringadeep-seavolcaniceruption(爆发)forthefirsttimeandthattheyplansimilarstudies.
Otherscientistshaveproposedtousethenetworkfortrackingoceancurrentsandmeasuringchangesinoceanandglobaltemperatures.
Thespeedofsoundinwaterisroughlyonemileasecond—slowerthanthroughlandbutfasterthanthroughair.Whatismostimportant,differentlayersofoceanwatercanactaschannelsforsounds,focusingtheminthesamewayastethoscope(听诊器)doeswhenitcarriesfaintnoisesfromapatient’schesttoadoctor’sear.Thisfocusingisthemainreasonthatevenrelativelyweaksoundsintheocean,especiallylow-frequencyones,canoftentravelthousandsofmiles.
31.Thepassageischieflyabout________.
A)anefforttoprotectanendangeredmarinespecies
B)thecivilianuseofamilitarydetectionsystem
C)theexposureofaU.S.Navytop-secretweapon
D)anewwaytolookintothebehaviorofbluewhales
32.Theunderwaterlisteningsystemwasoriginallydesigned________.
A)totraceandlocateenemyvessels
B)tomonitordeep-seavolcaniceruptions
C)tostudythemovementofoceancurrents
D)toreplacetheglobalradiocommunicationsnetwork
33.Thedeep-sealisteningsystemmakesuseof________.
A)thesophisticatedtechnologyoffocusingsoundsunderwater
B)thecapabilityofsoundtotravelathighspeed
C)theuniquepropertyoflayersofoceanwaterintransmittingsound
D)low-frequencysoundstravelingacrossdifferentlayersofwater
34.Itcanbeinferredfromthepassagethat________.
A)newradiodevicesshouldbedevelopedfortrackingtheendangeredbluewhales
B)bluewhalesarenolongerendangeredwiththeuseofthenewlisteningsystem
C)opinionsdifferastowhethercivilianscientistsshouldbeallowedtousemilitarytechnology
D)militarytechnologyhasgreatpotentialincivilianuse
35.WhichofthefollowingistrueabouttheU.S.Navyunderwaterlisteningnetwork?
A)Itisnowpartlyaccessibletocivilianscientists.
B)Ithasbeenreplacedbyamoreadvancedsystem.
C)Itbecameuselesstothemilitaryafterthecoldwar.
D)Itisindispensableinprotectingendangeredspecies
31.B32.A33.C34.D35.A
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