PassageThree
Inanagewhenwastetodaymeansalacktomorrow,makinguseofeveryavailableresourcebecomesmoreandmoreimportant.Ascoalisbeingusedingreaterandgreateramountstoproduceelectr icity,largeramountsofash,by-productofcoal,areproduced.Whencoalisburned
inaboiler,twokindsofashby-productareproduced,aheavybottomashandafine-as-powderflyashthatisfilteredandcapturedbyprecipitators.about10to15percentofthecoalby-productisbottomashwhichisusedlikesandonicycitystr eetsandhighwaysandalsoonhighwaysaspavingmaterial.Itistheflyash,however,thatisreceivingthegreateramountofattention.Flyashmaybeusedasanadditivetoconcreteintheconstr uctionofdams,bricks,androads,andcanreplaceupto20percentofthecementusedinconcrete.Asaby-productofburnedcoal,flyashrequiresnoadditionalexpenditureofenergytobeproduced,whilecementproductionrequiresgreatamountsofenergy.
Inadditiontousingflyashasaconcreteadditive,thetechnologyisavailabletoextr actthemainmineralcomponents-aluminum,silicon,andmagnetic.Today,extr actingthesecomponentsisaveryexpensiveprocess,butthetimemaycomewhenitischeapertoextr acttheseproductsfromashthantominenewsupplies.
41.Whatcanbeusedasamaterialtopaveroads?
A.Thecoalby-product.
B.Additive.
C.Fine-as-powderflyash.
D.BothBandC.
正确答案：A答案为A。根据题干找到第一段第三、四句，about10to15percentofthecoalby-productisbottomashwhichisusedlikesandonicycitystr eetsandhighwaysandalsoonhighwaysaspavingmaterial符合题意。
