英语四级考试长篇阅读练习试题.doc

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英语四级考试长篇阅读练习试题

英语四级长篇阅读练习试题原文：
Paper--MorethanMeetstheEye
A)Wearesurroundedbysomuchpaperandcardthatitiseasytoforgetjusthowplexitis.Therearemanyvarietiesandgradesofpapermaterials,andwhilstitisfairlyeasytospotthevarieties,itisfarmoredifficulttospotthegrades.
B)Itneedstobeunderstoodthatmostpaperandcardismanufacturedforaspecificpurpose,sothatwhilstthecorn-flakepacketmaylooksmart,itisclearlynotsomethingdestinedforthearchives.Itismadetolookgood,butonlyneedsalimitedlifespan.Itisalsomuchcheapertomanufacturethanhighgradecard.
C)Papercanbemadefromanalmostendlessvarietyofcellulose-basedmaterialwhichwillincludemanywoods,cottonsandgrassesorwhichpapyrusisanexleandfromwherewegetthewordpaper.Manyoftheseareveryspecialized,butthepreponderanceofpapermakinghasbeenfromsoftwoodandcottonorrags,withthebulkbeingwood-based.
PaperfromWood
D)Inordertomakewoodintopaperitneedstobebrokendownintofinestrands.Firstlybypowerfulmachineryandthenboiledwithstrongalkaliessuchascausticsoda,untilafinepulpofcellulosefibersisproduced.Itisfromthispulpthatthefinalproductismade,relyingonthebondingtogetherofthecelluloseintolayers.That,inaverysmallnutshell,istheessenceofpapermakingfromwood.However,therealityisrathermoreplicated.Inordertogiveusourwhitepaperandcard,themakerswilladdbleachandothermaterialssuchaschinaclayandadditionalchemicals.
E)Afurtherproblemwithwoodisthatitcontainsamaterialthatisnotcellulose.Somethingcalledlignin.Thisisessentialforthetreesinceitholdsthecellulosefibrestogether,butifitisincorporatedintothemanufacturedpaperitpresentsarchivistswithaproblem.Lignineventuallybreaksdownandreleasesacidproductsintothepaper.Thiswillweakenthebondbetweenthecellulosefibersandthepaperwillbeebrittleandlookratherbrownandcareworn.Wehaveallseenthisinoldnewspapersandcheappaperbackbooks.Ithasbeenestimatedthatmostpaperbackbookswillhavealifeofnotgreaterthanfiftyyears.Notwhatweneedforourarchives.
F)Sincethelignincanberemovedfromthepaperpulpduringmanufacture,theobviousquestioniswhyisitleftinthepaperTheans