【Itisonlyashinyyellowmetalbutitisoneofthemostvaluablethingsonearth.Sincethebeginningoftimemenhavelookedforthisextremelyvaluableitemgold.Goldissoftandeasytoformintodifferentobjects.】

　　Itisonlyashinyyellowmetalbutitisoneofthemostvaluablethingsonearth.Sincethebeginningoftimemenhavelookedforthisextremelyvaluableitemgold.

　　Goldissoftandeasytoformintodifferentobjects.Ifitgetswetitdoesnotrustlikeironorothermetals.Acids（酸）don'tchangeit.Oneimportantreasonwhygoldissovaluableisthatitisscarce.Becauseofitssoftnessgoldmustbecombinedwithothermetalsandsomakeithardenandgiveitstrength.Byhardeninggoldpeoplecanthenmakecoinsandjewelrywithit.Metalscommonlymixedwithgoldarenickel（镍）platinum（铂）andcopper.Goldjewelrybears（刻有）anumberandtheletterK.TheKmeanskarat(carat)whichisameasureoftheamountofpuregoldinthejewelry.Puregoldis24K.Thereforeanecklacewhichis14Kisfourteenpartsofgoldandtenpartsofothermetals.

　　Manycountriesmakeuseofgoldforcertaincoinsbutthispracticeisnotascommonnowasitoncewas.TheUnitedStatesforinstancestoppedmakinggoldcoinsin1933.

　　(1)Whichofthefollowingwouldbethebesttitleforthispassage?

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　　A．ValuableMetal.

　　B．LookingforGold.

　　C．JewelryandCoins.

　　D．WhatisKarat?

　　(2)Whichisnotthereasonwhygoldishighlyvaluable?

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　　A．Itcanbemadeintojewelry.

　　B．Itisnoteasilyfound.

　　C．Itissoftandshiny.

　　D．Itdoesn'trust（生锈）whenwet.

　　(3)Inordertomakeitstrongergoldisoftenmixedwith______.

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　　A．hardgold

　　B．coinsandjewelry

　　C．acids（酸）

　　D．othermetals

　　(4)Ifaringismarked12Kthenthepercentageofgoldis_____.

　　[]

　　A．12

　　B．50

　　C．25

　　D．24