【2015高考复习】任务型读写Ifyoucanfindatreewhichhasbeencutdown，youwillseemanyrings，orcircles，onthebaseofthetrunk.Bylearningtoreadtheserings，youcanfindoutaboutthetree'slife.Thenumberofringstellsyouhowoldthetreeis.Eachyear，newwoodisformedontheoutsideofthetree.Thisnewwoodislightincolorwhenthetreeisgrowinginspringandsummer，anddarkinwinterwhenthetreeisnotgrowingmuch.So，ifyoucounttheringsofdark­or­lightcoloredwood，youcanoftenfindouthowoldthetreeis.Youcanalsotellwhichyearshavebeengoodyearsandwhichyearshavebeenbadyears.Whenthelight­coloredringsareverywide，itmeansthatthetreehasbeengrowingquicklythatyear.Iftheringsarenarrow，ithasbeengrowingslowly.Iftheringsonatreetrunkweregreatlymagnified，youwouldbeabletoseewhytheringsarelight­coloredwhenthetreeisgrowingquicklyanddark­coloredwhenthetreeisgrowingslowly.Thetreetrunkismadeupofmicroscopictubes，likesomepipes，carryingwaterfromthesoil，throughthetrunk，anduptotheleaves.Theyarewideandthin­walledwhenthetreeisgrowingquicklyandtheyarecarryingalotofwater.Theyarenarrowandstucktogetherwhenthetreeisnotgrowingsoquickly.Whenatreeisold，thetubesinthecentreofthetreedon'tcarrywater.Thewallsofthetubeshavebecomethickwithmaterialswhichhavestuckalongthemovertheyears，formingakindofwoodcalled“heartwood”．Thiskindofwoodisdarkerincolorthantheyoung，growingwoodontheoutsideofthetree.Youdon'tveryoftenseewholetreetrunkswhichhavebeencutacross.Butonceyoulearntoreadacrosssectionofthewood，youcanseemuchmoreinwoodwhichhasbeenusedtomakeboxes，housesandotherthings.Inmostwood，insteadofseeingthetrunkcutacross，youareseeingitcutalongitslength.Becauseyoudon'tseethewholetree，youcan'ttellhowolditis.Title：__20__ofaTreeGeneralinformationOldtreesItemsFactsItemsFactsWherecanringsbeseenOnthe__21__ofatrunkThetubesinthecentreofthetreeDon'tcarrywaterThe__22__ofringsHelpsusknowaboutitsageThewallsofthetubesBecome__23__；Form__24____25__light­coloredringsShowthetreegrowsquicklyNarrow__26__ringsMeanthetreegrowsslowlyMicroscopictubesFunctionCarry__27__FeaturesWideand__28__whengrowingq