请认真阅读下列短文，从短文后各题所给的A、B、C、D四个选项中，选出最佳选项。

Ifadiversurfacestooquicklyhemaysufferthebends．Nitrogen(氮)dissolved(溶解)inhisbloodissuddenlyliberatedbythereductionofpressure．Theconsequenceifthebubbles(气泡)accumulateinajointissharppainandabentbody-thusthename．Ifthebubblesforminhislungsorhisbraintheconsequencecanbedeath．

Otherair-breathinganimalsalsosufferthisdecompression(减压)sicknessiftheysurfacetoofast：whalesforexample．Andsolongagodidichthyosaurs．Thattheseancientseaanimalsgotthebendscanbeseenfromtheirbones．Ifbubblesofnitrogenforminsidethebonetheycancutoffitsbloodsupply．Thiskillsthecellsintheboneandconsequentlyweakensitsometimestothepointofcollapse．Fossil(化石)bonesthathavecavedinonthemselvesarethusasignthattheanimaloncehadthebends．

BruceRothschildoftheUniversityofKansasknewallthiswhenhebeganastudyofichthyosaurbonestofindouthowwidespreadtheproblemwasinthepast．Whatheparticularlywantedtoinvestigatewashowichthyosaursadaptedtotheproblemofdecompressionoverthe150millionyears．Tothisendheandhiscolleaguestraveledtheworld'snatural-historymuseumslookingathundredsofichthyosaursfromtheTriassicperiodandfromthelaterJurassicandCretaceousperiods．

Whenhestartedheassumedthatsignsofthebendswouldberarerinyoungerfossilsreflectingtheirgradualevolutionofmeasurestodealwithdecompression．Insteadhewasastonishedtodiscovertheopposite．Morethan15％ofJurassicandCretaceousichthyosaurshadsufferedthebendsbeforetheydiedbutnotasingleTriassicspecimen(标本)showedevidenceofthatsortofinjury．

Ifichthyosaursdidevolveananti-decompressionmeanstheyclearlydidsoquickly-andmoststrangelytheylostitafterwards．ButthatisnotwhatDrRothschildthinkshappened．Hesuspectsitwasevolutioninotheranimalsthatcausedthechange．

Whalesthatsufferthebendsoftendosobecausetheyhavesurfacedtoescapeapredator(捕食动物)su