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1、雅思写作经典范文10篇（五）41AmericanblackbearsAmericanblackbearsappearinavarietyofcolorsdespitetheirname・Intheeasternpartoftheirrange,mostofthesebrown,red,orevenyeIlowcoats・Tothenorth,theblackbearisactua11ygrayorwhiteincolor・Eveninthesamelitter,bothbrownandblackfurr
2、edbearsmaybeborn・BlackbearsarethesmallestofalIAmericanbears,ranginginlengthfromfivetosixfeet,weighingfromthreehundredtofivehundredpoundstheireyesandearsaresmalIandtheireyesightandhearingarenotasgoodastheirsenseofsme11.LikealIbears,theblackbearistimid,clu
3、msy,andrarelydangerous,butifattacked,mostcanclimbtreesandcovergroundatgreatspeeds・Whenangryorfrightened,itisaformidableenemy.Blackbearsfeedonleaves,herbs.Fruit,berries,insects,fish,andevenlargeranimals.Oneofthemostinterestingcharacteristicsofbears,includ
4、ingtheblackbear,istheirwintersleep・Unlikesquirrels,woodchucks,andmanyotherwoodIandanimals,bearsdonotactuallyhibernate・Althoughthebeardoesnotduringthewintermoths,sustainingitselffrombodyfat,itstemperatureremainsalmostnormal,anditbreathesregularlyfourorfiv
5、etimesperminute.MostblackbearsIivealone,exceptduringmatingseason.Theyprefertoliveincaves,hoilowlogs,ordensethickets・AlittleofonetofourcubsisborninJanuaryorFebruaryafteragestationperiodofsixtoninemonths,andtheyremainwiththeirmotheruntiItheyarefullygrownor
6、aboutoneandahalfyearsold.BlackbearscanIiveaslongasthirtyyearsinthewiId,andevenlongeringamepreservessetasideforthem.41Coal-firedpowerplantsTheinventionoftheincandescentIightbulbbyThomasA.Edisonin1879createdademandforacheap,readilyavailablefuelwithwhichtog
7、eneratelargeamountsofelectricpower・Coalseemedtofitthebill,anditfueledtheearliestpowerstations・(whichweresetupattheendofthenineteenthcenturybyEdisonhimseIf)・AsmorepowerpIantswereconstructedthroughoutthecountry,thereIianceoncoalincreasedthroughoutthecountr
8、y,thereIianceoncoalincreased.SincetheFirstWorIdWar,coaI-firedpowerpIantshadacombinedintheUnitedStateseachyear・In1986suchpIantshadacombinedgeneratingcapacityof289,000megawattsandconsumed83percentofthenearly900milliontonsofc
