Didyouknowthatthenoiseinyourschoolyardcanharmyourhearingseriously?Duringbreaksatschool,youfindyourselfinthemiddleofloudactivitiesinthehallwaysandtheschoolyard.Youneedbreakstohavefunwithyourfriends,butyoushouldbecarefulasthenoiseatschoolcanbedangeroustoyourhearing.Herearesomeexamplesofschoolyardnoise:･Climbingthejunglegym(atadistanceof25meters):70-100dB(分贝);･Girlshouting(atadistanceof3meters):120dB;･Boyshouting(atadistanceof3meters):I20-130dB;･Studentsthrowingashovel(铁铲)onawoodenbox(atadistanceof1meter):135dBSomefactors(因素)decidehowharmfulanoiseistothehumanear:thedistancetothenoise,thelevelofthenoiseandthetimeitlasts.Wecanstandnoiseatthelevelof85dBforeighthoursaday.Butasthenoiseincreases,wecanonlystandthenoiseforshorterandshorterperiodsoftime.Whenthenoiselevelreaches115dB,ourearscanstanditforlessthan30secondsaday.Noiseatthelevelof130dBharmsyourhearingifyouhearitformorethanonesinglesecondaday.Ifyouwanttoenjoyyourbreaks,youshouldhelpkeepingthenoiseleveldown.1.Fromthepassage,weknowthat______factorsdecidehowharmfulanoiseistothehumanear.A.twoB.threeC.fourD.five2.Ourhearingwillnotbeharmedbynoise______.A.atthelevelof85dBfor12hoursadayB.atthelevelof115dBfor20secondsadayC.atthelevelof130dBfor5secondsadayD.atthelevelof135dBfor3secondsaday3.Whatisthemainideaofthepassage?A.Noiseatschoolcanreachveryhighlevels.B.Therearemanykindsofnoiseintheschoolyard.C.Studentsshouldn'thaveactivitiesintheschoolyard.D.Noiseatschoolcanbeveryharmfultostudents'hearing.4.Howmanyhourscanwestandnoiseatthelevelof85dBperday?A.fivehoursB.eighthoursC.fourhoursD.onehour（10.0分）