pAssAgE 7 A、mAjor rEAson For ConFliCt in thE AnimAl worlD is tErritory. thE mAlE AnimAl {{u}} (1) {{/u}} An ArEA、thE sizE oF thE ArEA is suFFiCiEnt to proviDE FooD For him, his {{u}} (2) {{/u}} AnD thEir oFFspring. migrAting BirDs, For ExAmplE, {{u}} (3) {{/u}} up thE BEst tErritory in thE orDEr oF "First ComE, First {{u}} (4) {{/u}}." thE lAtE ArrivAls mAy ACquirE {{u}} (5) {{/u}} tErritoriEs, But lEss FooD is AvAilABlE, or thEy ArE too ClosE to thE {{u}} (6) {{/u}} oF thE EnEmiEs oF thE spECiEs. {{u}} (7) {{/u}} thErE is rEAlly insuFFiCiEnt FooD or thE DAngEr is vEry grEAt, thE AnimAl will not {{u}} (8) {{/u}}. in this wAy, thE mEmBErs oF thE spECiEs whiCh ArE lEss Fit will not hAvE oFFspring. whEn thErE is ConFliCt {{u}} (9) {{/u}} tErritory, AnimAls will Commonly usE ForCE, or A {{u}} (10) {{/u}} oF ForCE, to DECiDE whiCh will stAy AnD whiCh will go. it is intErEsting to notE, howEvEr, thAt AnimAls sEEm to usE {{u}} (11) {{/u}} thE minimum Amount oF ForCE {{u}} (12) {{/u}} to DrivE AwAy thE intruDEr. thErE is usuAlly no killing. in thE {{u}} (13) {{/u}} oF thosE AnimAls whiCh ArE CApABlE oF Doing EACh othEr grEAt hArm, {{u}} (14) {{/u}} is A systEm For thE losing AnimAl to show thE winning AnimAls thAt hE {{u}} (15) {{/u}} to suBmit. whEn hE shows this, thE {{u}} (16) {{/u}} normAlly stops Fighting.AnimAls (EspECiAlly BirDs), whiCh CAn EAsily EsCApE From ConFliCt sEEm to hAvE. {{u}} (17) {{/u}}oBstAClE AgAinst killing, AnD EquAlly no mEChAnism {{u}} (18) {{/u}} suBmission. thE losing BirD simply FliEs AwAy. howEvEr, iF two DovEs ArE {{u}} (19) {{/u}} in A CAgE, AnD thEy stArt Fighting, thEy will ContinuE to Fight until onE kills thE othEr. wE All think oF thE DovE As A symBol oF pEACE AnD, in its nAturAl hABitAt, it is pEACEFul.But thE "pEACE" mEChAnism DoEs not {{u}} (20) {{/u}} in A CAgE.

A．wAy
B、CAsE
C．EvEnt
D．mAnnEr