资料：Ahigh-precisionNASAradarinstrumentleftaNASAairportinSouthernC

资料：Ahigh-precisionNASAradarinstrumentleftaNASAairportinSouthernCaliforniaforIcelandonJanuary28tocreatedetailedmapsofhowglaciersmoveinthedeadofwinter.Thiswillhelpscientistsaroundtheworldbetterunderstandsomeofthemostbasicprocessesinvolvedinmeltingglaciers,whicharemajorcontributorstorisingsealevels. NASAusedthesameairborneinstrumentinJune2012tomapthesummerflowsoftwoIcelandicicecaps.Theicecaps—largeareasofpermanentsnowandicecover—encompassmultipleglaciersflowingindifferentdirectionsandatdifferentspeeds.Bymappingthesameicecapsnow,inwinter,whenthesurfaceremainsfrozenallday,andthencomparingthewinterandsummervelocities,theresearcherswillbeabletoisolatetheeffectsofmeltwater. AboveisaviewofasmallpartoftheHofsjkullicecap,whichencompassesseveralglaciers.ThefanatupperleftispartofaglaciercalledMlaj?kull. Formoreontheresearch,seethisNASApressrelease. Howcanthescientistsfigureouttheeffectsofmeltingwater?

A.By melting the frozen iceberg in winter.

B.By observing the snow's moving directions.

C.By isolating ice from water in sunlines.

D.By comparing the glaciers moving speeds.

正确答案是D