【EyedoctorsinShanghaifoundoutthatthenearsightednessamongprimaryandmiddleschoolstudentshassomethingtodowiththecolourofthepaperintheirtextbooksandnotebooks．Thed】

　　   EyedoctorsinShanghaifoundoutthatthenearsightednessamongprimaryandmiddleschoolstudentshassomethingtodowiththecolourofthepaperintheirtextbooksandnotebooks．

　　   Thedoctorssuggestedthatyellowpaperwillbeusedtoreplacethewhiteone．Accordingto

　　theirresearch，theexpertsfoundoutwhitepaperreflectstoomuchlightandeasilytiresaperson’seyes．Theyellowpaper，however，doesn’tlooksosharptoaperson’seyes．Inotherwords，itismuchmildertotheeyesofstudentswhomaydoreadingorwritingforhours． 

　　Theexperts’researchfindingswerebasedonfirst．handinformationandanumberofscientificexperimentsincludinganewstudyamongthestudentsfromforty-onemiddleschools．Tomakethestudentsunderstandthetruth，ShanghaiEducationDevelopmentCo．Ltd．hasproducedtextbooksandexercise．booksmadeofyellowpaper．Thebookswillbeusedinthewholecitysoon．

　　(   )49．Whatdoestheword“replace”heremeaninChinese?

　　       A．放置          B．重置         C．替代        D．发生

　　(   )50．Thedoctorsfoundout_________causedthestudents’nearsightedness．

　　       A．theirstudieshave                 B．thecolourofthepaperhas

　　       C．thetextbooksandnotebookshave    D．thecolouroftheirclotheshas

　　(   )51．Whydoeswhitepapereasilymakeoureyestired?

　　       A．Becausewhitepaperreflectstoomuchlight．

　　       B．Becausewhitepapergetsintoomuchlight．

　　       C．Becausewhitepaperisalwaysshining．

　　    D．Becausewhitepaperistoobright．