EricaDavidlivesinPinedale，Wyoming，USA，wherewintercanbringtemperaturesofbelow35degreesFahrenheit，howlingwinds，andalotofsnow．Soitwasjustnaturalthatshechosetostudysnowforherschoolsciencefairinthesixthgrade
EricaDavidlivesinPinedale，Wyoming，USA，wherewintercanbringtemperaturesofbelow35degreesFahrenheit，howlingwinds，andalotofsnow．Soitwasjustnaturalthatshechosetostudysnowforherschoolsciencefairinthesixthgrade．
Nowajuniorinhighschool，Ericaisinhersixthyearofsnowexperiments，andiswellonherwaytobecomingasnowexpert．Shestartedwithabasicquestion：Couldsnowfencesbebuilttoworkbetter？
Snowfencesareusedtokeepsnowdrifts（雪堆）fromcoveringareaslikeroadsoftraintracks，ortohelpbuildupsnowwhereitcanhelpwithwatershortagesinspringwhenitmelts（融化）．"Also，Iwantedtoprotectmyanimalsbetterfromblowingsnow，"saysErica，whoraisesgoats，sheep，andpigs．
Beforeshecouldtestfencedesigns，Ericahadtofigureoutwhatwouldactlikerealsnowinherexperiments．"Itestedflour，sugar，andsaltbeforeIsettledondishwasherpowder，"sheexplains．
Sciencefairsofferstudentsthechancetotesttheories，presentfindingstojudges，andmeetotherresearchers．Erica'smanyachievementsincludecompetingattheDiscoveryChannelYoungScientistChallengeformiddleschoolstudentsandtheIntelInternationalScienceandEngineeringFair，wherestudentsfromaroundtheworldpresenttheirscienceresearch．
Butperhapsthebestrewardisthatherresearchisalreadybeingputtogooduse．Shehascomeupwithanimprovedsnowfencedesign，andthisyearshe'shelpingthinkouthowtoprovidewatersupplytonativeplants，whichhavebeenkilledoffbydrillingatnearbynaturalgasfields．
"Sciencefairsareanamazingexperience，"saysErica．"Justpickyourtruefeelingandgoforit．"
72．Whatdoesthepassagesuggesttous？___
A．SciencefairsareheldforhighschoolstudentsinAmerica．
B．EricaistheyoungestshowexpertwellknowninAmerica．
C．TheenvironmentbroughtmuchconvenienceforEricatostudysnow．
D．ThehopetocontributetoherhometownmadeEricaexperimentonsnow．
73．InErica'shometown，snowfencesmayplayapartin___．
a．reducingtheharmblowingsnowdoestoanimals
b．supplyingwaterresourcetothenearbygasfields
c．makingu