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1、ZQ国田IELTSADVANTAGESentenceCompletionPaSSage1ClassesofTreesintheUSAThetimberoftheUnitedStatesisfurnishedbythreewell-definedclassesoftrees:(1)theneedle-leaved,naked-seededconifers,suchaspinezcedarzetc.,(2)thebroad-leavedtreessuchasoak,POPIai;etc.,and(3)toaninferiorextentbythe(one-seedleaf)palmszyuccas
2、,andtheirallies,whichareconfinedtothemostsouthernpartsofthecountry.Broad-leavedtreesarealsoknownasdeciduoustrees,although,especiallyinwarmcountries,manyofthemareevergreen,whiletheneedle-leavedtrees(conifers)arecommonlytermedevergreens,althoughthelarch,baldcypress,andothersshedtheirleaveseveryfall,an
3、deventhenamesbroad-leavedandconiferous,thoughperhapsthemostsatisfactory,arenotatallexact,fortheconiferginkgohasbroadleavesandbearsnocones.Amongthewoodsmen,thewoodsofbroad-leavedtreesareknownashardwoods,thoughpoplarisassoftaspinezandtheconiferouswoodsareknownassoftwoods,notwithstandingthefactthatyewr
4、ankshighinhardnessevenwhencomparedwithhardwoods.Bothinthenumberofdifferentkindsoftreesorspeciesandstillmoreintheimportanceoftheirproducttheconifersandbroad-leavedtreesfarexcelthepalmsandtheirrelatives.Inthemanneroftheirgrowth,boththeconifersandbroad-leavedtreesbehavealike,addingeachyearanewlayerofwo
5、od,whichcoverstheoldwoodinallpartsofthestemandlimbs.Thus,thetrunkcontinuestogrowinthicknessthroughoutthelifeofthetreebyadditions(annualrings),whichintemperateclimatesare,barringaccidents,accuraterecordsofthetreesage.Withthepalmsandtheirrelativesthestemremainsgenerallyofthesamediametecthetreeofahundr
6、edyearsoldbeingasthickasitwasattenyearszthegrowthofthesebeingonlyatthetop.Evenwhereaperipheralincreasetakesplace,asintheyuccas,thewoodisnotlaidoninwell-definedlayersforthestructureremainsirregularthroughout.Thoughalikeinthemanneroftheirgrowth,andthereforesimilarintheirgeneralmake-up,conifersandbroad
7、-leavedtreesdiffermarkedlyinthedetailsoftheirstructureandthecharacteroftheirwood.Thewoodofallconifersisverysimpleinitsstructure,thefibrescomposingthemainpartofthewoodallbeingalikeandtheirarrangementregular.Thewoodofthebroad-leavedtreesiscomplexinstructure;itismadeupofdifferentkindsofcellsandfibresan
8、dlackstheregularityofarrangementsonoticeableintheconifers.Thisdifferenceissogreatthatinastudyofwoodstructureitisbesttoconsiderthetwokindsseparately.Inthiscountrythegreatvarietyofwoods,andespeciallyofusefulwoods,oftenmakesthemeredistinctionofthekindorspeciesoftreemostdifficult.Thus,thereareatleasteig
9、htpinesofthethirty-fivenativeonesonthemarket,someofwhichsocloselyresembleeachotherintheirminutestructurethatonecanhardlytellthemapart,andyettheydifferinqualityandareoftenmixedorconfoundedinthetrade.Ofthethirty-sixoaks,ofwhichprobablynotlessthansixoreightareQD国IELTSADVANTAGESentence Completionmarkete
10、d,wecanreadilyrecognizebymeansoftheirminuteanatomyatleasttwotribes-thewhiteandblackoaks.Thesameistrueoftheelevenkindsofhickory,thesixkindsofashzandsoon.ThelistofnamesofalltreesindigenoustotheUnitedStates,asenumeratedbytheUnitedStatesForestService,is495innumber,thedesignationoftreebeingappliedtoallwo
11、odyplantswhichproducenaturallyintheirnativehabitatonemain,erectstem,bearingadefinitecrown,nomatterwhatsizetheyattain.TimberisproducedonlybytheSpermatophyta,orseed-bearingplants,whicharesubdividedintotheGymnosperms(conifers),andAngiosperms(broad-leaved).Theconiferorcone-bearingtree,towhichbelongthepi
12、nes,Iarcheszandfirs,isoneofthethreenaturalordersofGymnosperms.Thesearegenerallyclassedassoftwoods,andaremoreextensivelyscatteredandmoregenerallyusedthananyotherclassoftimber,andaresimpleandregularinstructure.Theso-calledhardwoodsareDicotyledonsorbroad-leavedtrees,asubdivisionoftheAngiosperms.Theyare
13、generallyofslowergrowth,andproducehardertimberthantheconifers,butnotnecessarilyso.Basswood,poplar;sycamorezandsomeofthegums,thoughclassedwiththehardwoods,arenotnearlyashardassomeofthepines.Source:https:WWW.autenberq.orci/files/26598/26598-h/26598-h.htm#SEenONIQuestions11-14Completethesentencesbelow.
14、ChooseNOMORETHANONEWORDfromthetextforeachanswer.Writeyouranswersinboxes11-14onyouranswersheet.11. Thebroad-leafedconiferknownas_hasnocones.12. Everyyearthetrunksofconifersandbroad-leavedtreesgetthickerbyadding_whichcanbeusedtotellhowoldthetreeis.13. The_whichconiferwoodiscomposedofareallsimilarandregularlyarranged.14. Oaksareseparatedinto_andblackvarieties.
