请阅读Passage2，完成第小题。 Passage2 AmongChina'sgreatestarttreasuresaretheBuddhistcavesnearDunhuang.Theirancientfrescoesandsculptureshavesurvivedwars,environmentaldamage,antiquitieshunters,andthechaoticCulturalRevolution. Todaydomestictourismisthebiggestthreat:theUNESCOWorldHeritagesitehasanoptimalcapacityof3,000perday,butpeaktimescanseetwicethatmanyvisitors. TheMogaoGrottoesareespeciallyvulnerabletomasstourism.Theirecosystemsarefragile.Abuildupofhumidityandcarbondioxidefromvisitors'breathcanleadtoflakinganddiscolorationofwallpaintings. Topreservethecaves,theDunhuangAcademyispioneeringaprojecttodigitizethesite. Recently,theArthurM.SacklerGalleryinWashington, D. C.,offeredatantalizingglimpseattheundertaking.Donning3-Dglasses,visitorsweretransportedintoabreathtaking"virtual"Dunhuanggrotto,knownasCave220.The3-D,interactiveexperienceisfloodedwithvividcolor,close-updetails,movingimagesofflyingbodhisattvas,evensound,"DunhuangranksasthesinglemostimportantrepositoryofearlyChineseart.HerethegreatculturesoftheWorld--GreekandRoman,PersianandMiddleEastern,IndianandChinese--constantlyinteractedforoveramillennium,"saidMimiGates,whoformedtheDunhuangFoundation."High-resolutiondigitizationwillprovidealastingrecordofthisartistictreasureforallmankindandcanmakeitaccessiblebeyondChina." Adozenyearsago,theDunhuangAcademybegancooperatingwithforegoinginstitutionstoconservethetreasures.Amongtheprojects,oneusedacameratocreateadigitalarchiveofthecaves.Theresultswillbeusedintheacademywhichplanned＄40millionstate-of-the-artvisitorcenterwhichwillpresentvirtualtourofthecavestosavetherealsitewearandtear.Thescopeoftheprojectisdaunting.Itrequires20minutesorsotorecorda9-square-meterfresco,andthereare492caveswithmuralsinside.ButtheSacklerexhibitprovedhowenthrallingthesinglevirtualcaveCaBbe. Realcavesprovidenolightbulbs.Oncetheyreachcriticallevelsofmoistureandtemperature,theyareshuttothepublic.Onlyafewdozencavesareaccessibleatanygiventime.ButtheSackler'svirtualtourwasdifferent.Oneofthemostpopularfeatureswasthe"magnifyingglass",whichcanzoominon,say,azitherdepictedinamural.Theinstrumentappearstopopoutofthewall,enlarge,andthenrotateinspace.Visitorscanalso"flip"backandforthbetweentheintricateTang-dynastymuralandalater,cruderSung-dynastyfresco. TohelpCave220'sTangdancerpaintingsmagicallycometolife,twoChineseperformerswereflowntotheAppliedLaboratoryforInteractiveVisualizationandEmbodiment(ALIV E)inaHongKonguniversity.Forthreedaysthedancerswerefilmedperformingintricatesteps,fluidmovements,andcarefulmanipulationoflong,sinuousribbons.TheyappearedintheSacklertour,dancingasifinmidair,cladinbrightlycoloredTangcostume.ALIVE'sprojectmanagersaidwhilehe'sbecomeintimatelyfamiliarwiththeimagesCave220,hehasn'tbeenthereyet."Ican'twaittovisittherealthing." WhichofthefollowingfactorsmentionedinthearticlemaycauseaseveredamagetotheBuddhistcavestoday? 查看材料
A.Antiquities hunters. B.Environmental damage. C.The optional number of tourists. D.Visitors exceeding the optimal number.正确答案D
