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1、2019-2020年高三11月周考英语试题缺答案（时间120分钟，满分150）xx.11第Ⅰ卷（共70分）Ⅱ.Grammarandvocabulary（20%）SectionADirections:Afterreadingthepassagesbelow,fillintheblankstomakethepassagescoherentandgrammaticallycorrect.Fortheblankswithagivenword,fillineachblankwiththeproperform
2、ofthegivenword;fortheotherblanks,useonewordthatbestfitseachblank.Inmostindustrializedcountriesabout105boysarebornforevery100girls,foraratioof1.05,knownasthesecondarysexratio,orSSR;theprimarysexratioistheratioatconception.Thisisoftenexpressedastheperce
3、ntageofboysamongallbirths,orabout51.2percent.Thepercentageofmalesamongallbirthsisnotfixed,however.Sincethe1950sand1960stheoverallSSR25(decline)intheU.S.,CanadaandseveralEuropeancountries,therearealsobothpersonalandenvironmentalfactorsthataffecttheaver
4、agesexratio.26chanceofhavingaboyappears27(decline)withthemother'sage,thefather'sageandthenumberofchildrenthefamilyalreadyhas.Theseeffectsaresmall.OnestudyinDenmarkfoundthattheSSRofchildrenborntofathersyoungerthan25was51.6percent,whichdecreased2851.0pe
5、rcentamongchildrenoffathersatleast40yearsofage.ThereforeitisunlikelythatthedecliningSSRinmanycountriesresultssolelyfromlarge-scalechangesinsuchpersonalfactors.Withregardtoenvironmentalfactors,improvedprenatalandobstetricalcareduringthefirstpartofthe20
6、thcenturyislargelyresponsibleforan29(increase)SSRoverthisperiodinmanycountries.Themalefetusismoresusceptibletolossinthewombthanisthefemalefetus,sowithmoreconceptionsreachingterm,proportionallymoremalesareborn.Itisdifficulttodiscernhowmuchofthedecrease
7、insexratiosincethe1950sarisesfromcontaminantsintheenvironment.Whatisknownisthatdruguse,highoccupationalexposuresandenvironmentalaccidents30affectSSR.Forexample,hopefulmothers31(take)clomiphenecitrate(Clomid)forinfertilityborebabieswithanSSRofonly48.5p
8、ercent.Workersproducing1,2-dibromo-3-chloropropane(DBCP),achemicalusedtokillwormsinagriculture,experiencedevenlargerdecreasesinthenumberofmalebabies.EffectsofDBCPonspermquality32(discover)incidentallywhenmaleworkersfoundthattheywereunabletofat
