Theoceanbottomaregionnearly2．5timesgreaterthanthetotallandareaoftheEarthiseventodaylargelyunexplored．Untilaboutacenturyagothedeep-oceanfloorwascompletelyinaccessibleandhiddenbeneathwatersaveragingover3600metersdeep．TotallywithoutlightandsubjectedtointensepressureshundredsoftimesgreaterthanattheEarth’ssurfacethedeep-oceanbottomisastrangeenvironmenttohumansinsomewaysasforbiddingandremoteastheouterspace．

Althoughresearchershavetakensamplesofdeep-oceanrocksforoveracenturythefirstdetailedglobalstudyoftheoceanbottomdidnotactuallystartuntil1969withthebeginningoftheNationalScienceFoundation’sDeepSeaDrillingProject(DSDP)．UsingtechniquesfirstdevelopedfortheoffshoreoilandgasindustrytheDSDP’sdrillshiptheGlomarChallengerwasabletomaintainasteadypositionontheocean’ssurfaceanddrillinverydeepwaterstakingsamplesof rockfromtheoceanfloor．

TheGlomarChallengercompleted96voyagesina15-yearresearchprogramthatendedinNovember1983．Duringthistimeitsailed600000kilometersandtookalmost20000samplesofrocksaroundtheworld．ThosesampleshaveallowedgeologiststoreconstructwhattheplanetlookedlikehundredsofmillionsofyearsagoandtomakeoutwhatitwillprobablylooklikemillionsofyearsinthefutureTodaylargelyonthestrengthofevidencegatheredduringtheGlomarChallenger’svoyagesnearlyallearthscientistsagreeonthetheoriesofplatetectonics（构造学）andcontinentaldriftthatexplainmanyofthegeologicalprocesses．

ThesamplesofrocksdrilledbytheGlomarChallengerhavealsoprovidedaclimaticrecordstretchingbackhundredsofmillionsofyears．Theinformationofpastclimaticchangecanbeusedtopredictfutureclimates．

68．Whatdoestheunderlinedword“inaccessible”inline3means?

A．unrecognizable B．unreachable C．unusable D．unreasonable

69．Whydoestheauthormention“outerspace”inthefirstparagraph?

A．TheEarth’sclimatemillionsofyearsagowassimilartothatinouterspace．

B．Itissimilartotheoceanfloorinbeingstrangetothehumans．

C．Rockformationsinouterspacearesimilartothosefoundontheocean