pAssAgE 1 ovEr An ExtEnDED pErioD oF timE it is possiBlE For potEntiAl Firms to EntEr or For Existing Firms to lEAvE A CompEtitivE inDustry. in thE CompEtitivE worlD, shiFts in thE proDuCtivE {{u}} (1) {{/u}} oF thE EConomy From Any onE linE oF proDuCtion to othErs woulD {{u}} (2) {{/u}} in this wAy. thE lEngth oF thE timE pErioD {{u}} (3) {{/u}} For Entry AnD/or Exit will vAry, DEpEnDing upon thE {{u}} (4) {{/u}} involvED、somE, likE hot Dog stAnDs, mAy BE EAsily AnD quiCkly {{u}} (5) {{/u}}. othErs, likE tExtilE mills, will rEquirE A longEr plAnning AnD ConstruCtion pErioD、whAtEvEr thE timE {{u}} (6) {{/u}} nECEssAry For Firms to EntEr or Exit A givEn inDustry, wE {{u}} (7) {{/u}} thAt pErioD As thE long run For thAt inDustry. For DiFFErEnt inDustriEs, thE long run will EnCompAss DiFFErEnt timE spAns. thE ForCE thAt {{u}} (8) {{/u}} thE Entry oF nEw Firms into An inDustry is proFit {{u}} (9) {{/u}} . whEn thE Firms in An inDustry ArE mAking proFits, thEy proviDE thE invEstors in thosE Firms with highEr-thAn-AvErAgE rEturns on thEir invEstmEnts. highEr-thAn-AvErAgE rEturns sElDom go {{u}} (10) {{/u}}. in thE long run thEy AttrACt nEw invEstmEnt AnD nEw Firms. on thE othEr hAnD, lossEs proviDE thE {{u}} (11) {{/u}} For Firms in An inDustry to lEAvE it. lossEs mEAn thAt rEturns to invEstors in thE inDustry ArE BElow thE AvErAgE rECEivED By invEstors EConomy-wiDE; howEvEr, thEy Do not nECEssArily {{u}} (12) {{/u}} thAt thE nEt inComE oF thE Firm is {{u}} (13) {{/u}}. it mAy or it mAy not BE.But invEstors will wAnt to withDrAw thEir invEstmEnts From thE loss-inCurring inDustry AnD {{u}} (14) {{/u}} in othEr inDustriEs whErE thE rEturns will BE grEAtEr. whErE proFits Exist, rEturns on invEstmEnt ArE ABovE AvErAgE. whErE lossEs oCCur, rEturns ArE BElow AvErAgE. so invEstmEnt is {{u}} (15) {{/u}} BEing rEDirECtED From lEss vAluABlE to morE vAluABlE usEs.

A．rEstorE
B．rEplACE
C．rEnEw
D．rEinvEst