问题详情

C
LifeintheClear
Transparentanimalsletlightpassthroughtheirbodiesthesamewaylightpassesthroughawindow.Theseanimalstypicallylivebetweenthesurfaceoftheoceanandadepthofabout3，300feet—asfarasmostlightcanreach.Mostofthemareextremelydelicateandcanbedamagedbyasimpletouch.SonkeJohnsen，ascientistinbiology，says，“Theseanimalslivethroughtheirlifealone.Theynevertouchanythingunlessthey’reeatingit，orunlesssomethingiseatingthem.”
Andtheyareasclearasglass.Howdoesananimalbecomesee-through？It’strickierthanyoumightthink.
Theobjectsaroundyouarevisiblebecausetheyinteractwithlight.Lighttypicallytravelsinastraightline.Butsomematerialsslowandscatter(散射)light，bouncingitawayfromitsoriginalpath.Othersabsorblight，stoppingitdeadinitstracks.Bothscatteringandabsorptionmakeanobjectlookdifferentfromotherobjectsaroundit，soyoucanseeiteasily.
Butatransparentobjectdoesn’tabsorborscatterlight，atleastnotverymuch，Lightcanpassthroughitwithoutbendingorstopping.Thatmeansatransparentobjectdoesn’tlookverydifferentfromthesurroundingairorwater.Youdon’tseeit————youseethethingsbehindit.
Tobecometransparent，ananimalneedstokeepitsbodyfromabsorbingorscatteringlight.Livingmaterialscanstoplightbecausetheycontainpigments(色素)thatabsorbspecificcolorsoflight.Butatransparentanimaldoesn’thavepigments，soitstissueswon’tabsorblight.AccordingtoJohnsen，avoidingabsorptionisactuallyeasy.Therealchallengeispreventinglightfromscattering.
Animalsarebuiltofmanydifferentmaterials————skin，fat，andmore————andlightmovesthrougheachatadifferentspeed.Everytimelightmovesintoamaterialwithanewspeed，itbendsandscatters.Transparentanimalsusedifferenttrickstofightscattering.Someanimalsaresimplyverysmallorextremelyflat.Withoutmuchtissuetoscatterlight，itiseasiertobesee—through.Othersbuildalarge，clearmassofnon-livingjelly-lie(果冻状的)materialandspreadthemselvesoverit.
Largertransparentanimalshavethebiggestchallenge，becausetheyhavetomakeallthedifferenttissuesintheirbodiesslowdownlightexactlyasmuchaswaterdoes.Theyneedtolookuniform.Buthowthey’redoingitisstillunknown.Onethingisclearfortheselargeranimals，stayingtransparentisanactiveprocess.
63.AccordingtoParagraph1，transparentanimals_______.
A.stayingroups
B.canbeeasilydamaged
C.appearonlyindeepocean
D.arebeautifulcreatures
请帮忙给出正确答案和分析，谢谢！