【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_____.
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A．12
B．50
C．25
D．24
