完型填空。Throughouthistorymanhashadtoacceptthefactthatalllivingthingsmustdie.Butpeoplenowlivelongerthanthey1.Yet,alllivingthingsstillshowthe2ofaging,whichwilleventually3death.

　　完型填空。 Throughouthistorymanhashadtoacceptthefactthatalllivingthingsmustdie.Butpeoplenowlive

　　longerthanthey 1 .Yet,alllivingthingsstillshowthe 2 ofaging,whichwilleventually 3 death.

　　Agingisnotadisease,butasapersonpassesmaturity(成熟期),thecellsofthebodyandthe 3

　　theyformdonotfunctionaswellasthey 5 inchildhoodandteenageyears.Thebodyprovidesless 6 againstdiseaseandismore 7 tohaveanaccident.

　　Anumberofrelatedcausesmay 8 toaging.Somecellsofthebodyhaveafairlylonglife,butthey

　　arenot 9 whentheydie.Asapersonages, 10 ofbraincellsandmusclecellsdecreases. 11 body

　　cellsdieandarereplacedbynewcells.Inanagingpersonthe 12 cellsmaynotbeasworkableoras

　　capable 13 growthasthoseofayoungperson.

　　Another 14 inagingmaybechangeswithinthecells 15 .Someoftheproteinchemicalsincellsareknown 16 withageandbecomelesselastic(有弹性).Thisiswhytheskinofoldpeoplewrinklesand

　　17 .Thisisalsothereasonwhyoldpeople 18 inheight.Theremaybeothermoreimportantchemicalchangesinthecells.Somecomplexcellchemicals,suchasDNAandRNA,storeand 19 information

　　thatthecellsneed.Agingmayaffectthis 20 andchangetheinformationcarryingmoleculessothatthey

　　donottransmittheinformationaswell.( )1．A.would

　　( )2．A.function

　　( )3．A.leadin

　　( )4．A.hands

　　( )5．A.do

　　( )6．A.energy

　　( )7．A.likely

　　( )8．A.attend

　　( )9．A.replaced

　　( )10．A.anumber

　　( )11．A.Theothers

　　( )12．A.old

　　( )13．A.to

　　( )14．A.factor

　　( )15．A.forthemselves

　　( )16．A.change

　　( )17．A.hangsloose

　　( )18．A.increase

　　( )19．A.passaway

　　( )20．A.improvement B．beusedto

　　B．effect

　　B．givein

　　B．feet

　　B．hasdone

　　B．protection

　　B．probable