题目内容：
Questionsarebasedonthefollowingpassage． Ifyouthinkahigh-factorsunscreen(防晒霜)keepsyousafefromharmfulrays,youmaybewrong．Researchinthisweek'sNatureshowsthatwhilefactor50reducesthenumberofmelanomas(黑瘤)anddelaystheiroccurrence,itcan'tpreventthem．Melanomasarethemostaggressiveskincancers．Youhaveahigherriskifyouhaveredorblondhair,fairskin,blueorgreeneyes,orsunburneasily,orifacloserelativehashadone．Melanomasaremorecommonifyouhaveperiodicintenseexposuretothesun．Otherskincancersareincreasinglylikelywithlong-termexposure．
Thereiscontinuingdebateastohoweffectivesunscreenisinreducingmelanomastheevidenceisweakerthanitisforpreventingothertypesofskincancer．A2011Australianstudyof1,621peoplefoundthatpeoplerandomlyselectedtoapplysunscreendailyhadhalftherateofmelanomasofpeoplewhousedcreamasneeded．Asecondstudy,comparing1,167peoplewithmelanomasto1,101whodidn'thavethecancer,foundthatusingsunscreenroutinely,alongsideotherprotectionsuchashats,longsleevesorstayingintheshade,didgivesomeprotection．Thisstudysaidotherformsofsunprotectionnotsunscreenseemedmostbeneficial．Thestudyreliedonpeoplerememberingwhattheyhaddoneovereachdecadeoftheirlives,soit'snotentirelyreliable．Butitseemsreasonabletothinksunscreengivespeopleafalsesenseofsecurityinthesun．
Manypeoplealsodon'tusesunscreenproperlyapplyinginsufficientamounts,failingtoreapplyafteracoupleofhoursandstayinginthesuntoolong．Itissunburnthatismostworryingrecentresearchshowsfiveepisodesofsunburnintheteenageyearsincreasestheriskofallskincancers．
Thegoodnewsisthatacombinationofsunscreenandcoveringupcanreducemelanomarates,asshownbyAustralianfiguresfromtheirslip-slop-slapcampaign．Soifthereisaheatwavethissummer,itwouldbebestforus,too,tosliponashirt,slopon(抹上)sunscreenandslaponahat．
Whatispeople'scommonexpectationofahigh-factorsunscreen? A．Itwilldelaytheoccurrenceofskincancer．
B．Itwillprotectthemfromsunburn．
C．Itwillkeeptheirskinsmoothandfair．
D．Itwillworkforpeopleofanyskincolor．
参考答案：
答案解析：