{{B}}DirECtions:{{/B}}
rEAD thE Following tExt.ChoosE thE BEst worD(s) For EACh numBErED BlAnk AnD mArkA,B,C、orD、onAnswEr shEEt 1.

in his 1979 Book, thE sinkingArk, Biologist normAn myErs EstimAtED thAt {{u}} (1) {{/u}} oF morE thAn 100 humAn-CAusED ExtinCtions oCCur EACh ClAy, AnD thAt onE million spECiEs {{u}} (2) {{/u}} By thE CEntury’s EnD、yEt thErE is littlE EviDEnCE oF {{u}} (3) {{/u}} thAt numBEr oF ExtinCtions. For ExAmplE, only sEvEn spECiEs on thE {{u}} (4) {{/u}} spECiEs list hAvE BEComE ExtinCt {{u}} (5) {{/u}} thE list wAs CrEAtED in 1973. Bio- {{u}} (6) {{/u}} is An importAnt vAluE, ACCorDing to mAny sCiEntists. nEvErthElEss, thE supposED mAss ExtinCtion rAtEs BAnDiED ABout ArE {{u}} (7) {{/u}} By multiplying {{u}} (8) {{/u}} By improBABlEs to gEt imponDErABlEs. mAny EstimAtEs, For instAnCE, rEly A grEAt DEAl on A "spECiEs-ArEA {{u}} (9) {{/u}} ", whiCh prEDiCts thAt twiCE As mAny spECiEs will BE FounD on 100 squArE milEs {{u}} (10) {{/u}} on tEn squArE milEs. thE proBlEm is thAt spECiEs ArE not DistriButED {{u}} (11) {{/u}} , so Bow muCh oF A ForEst ArE DEstroyED mAy BE As importAnt As {{u}} (12) {{/u}} . {{u}} (13) {{/u}} , sAysAriEl lugo, DirECtor oF thE intErnAtionAl institutE oF tropiCAl ForEstry in puErto riCo, "Biologists who prEDiCt high {{u}} (14) {{/u}} rAtEs {{u}} (15) {{/u}} thE rEsiliEnCy oF nAturE". onE oF thE mAin musEs oF ExtinCtions is DEForEstAtion.ACCorDing to thEConsultAtivE group on intErnAtionAlAgriCulturAl rEsEArCh, whAt DEstroys tropiCAl trEEs is not CommErCiAl logging, {{u}} (16) {{/u}} "poor FArmErs who hAvE no othEr {{u}} (17) {{/u}} For FEEDing thEir FAmiliEs thAn slAshing AnD Burning A {{u}} (18) {{/u}} oF ForEst". in CountriEs thAt prACtiCE moDErn {{u}} (19) {{/u}} AgriCulturE, ForEsts ArE in {{u}} (20) {{/u}} DAngEr. in 1920, u. s. ForEsts CovErED 732 million ACrEs. toDAy thEy CovEr 737 million.

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