【SomewonderfullycreativeusesofX-rayshavebeenintheworldofart．Butthemostimpressiveoneistouncoverwhathasbeencoveredup．DetailsunfoldedbyanX-rayofapaintingcan'tbeseenanyotherway．Forexampleinthepast】

　　SomewonderfullycreativeusesofX-rayshavebeenintheworldofart．Butthemostimpressiveoneistouncoverwhathasbeencoveredup．DetailsunfoldedbyanX-rayofapaintingcan'tbeseenanyotherway．Forexampleinthepastpaintingswereoftenrepairedifsmallpiecesofpaintfelloffthecanvas（帆布）．Theserepairscannotbeseenjustbylookingatthepainting．IttakesanX-raytodiscoverwheretherepairshavebeenmade．

　　AnX-rayofapaintingisoneofthebestwaystotellifitwascreatedbyafamouspainterorifitisaforgery（赝品）．IfthereisaquestionastowhetheranoldmasterhaspaintedacertainpaintingornotX-raysaremadeandcomparedtothoseofpaintingsthatareknowntobeoriginal．Ifthebrushstrokes（笔迹）forexampleareshowntobetotallydifferentthaninotherworkdonebyacertainartistthenthepaintingisprovedtobeafakecopy．

　　SincemodernpaintsareusuallymadefromdifferentmaterialsthanpaintsofhundredsofyearsagotheimagetheyleaveonanX-rayfilmlooksdifferent．ThisisanotherwayX-rayscanbeusedtospotaforgery．Amodemartistwilltrytomakeaforgerylookhundredsofyearsoldbypaintingdirtyvarnishonitorbyusingartificialmeanstogetthevarnishtolookcracked．TothenakedeyetheforgerymaylookoldbutwhenacarefulstudyoftheX-rayimageismadethedeceptionisobvious．

　　Itwascommonmanyyearsagoforanartisttofinishapaintingdecideitwasn'tanygoodandpaintacompletelydifferentpictureontopofit．Orartistswouldpaintoverothers'work—itwastheirversionofrecycling．TakinganX-rayistheonlywaytofindoutifthereisapictureunderneaththepictureyouseewithyoureyes．Sometimesmuseumswillbemoreinterestedinthepaintingbeneaththantheoneontopandwillrestoretheolderonebyhavingthetoplayerpainstakinglyremoved．

　　1.Whatisthemainpurposeofthearticle?

　　A．Toprovideinformationtopolicewhoarelookingforstolenart．

　　B．Topersuadeartdealerstocheckforfakecopiesbeforesellingart．

　　C．Toexplainhowmoderntechnologycanbeappliedinuniqueways．

　　D．Tohelpartistsrestoredamagedartworktoitsoriginalappearance．

　　2.Accordingtothepassage，X-raysareusedto______．

　　A．makerepairsonpaintingsinthepast

　　B．ident