Inaworldwhereitseemswealreadyhavetoomuchtodo,andtoomanythingstothinkabout,itseemsthelastthingweneedissomethingnewthatwehavetolearn.Butusecasesdosolveaproblemwithrequirements:with__1__declarativerequirementsit'shardtodescribestepsandsequencesofevents.Usecases,statedsimply,allowdescriptionofsequencesofeventsthat,takentogether,leadtoasystemdoingsomethinguseful.Assimpleasthissounds,thisisimportant.Whenconfrontedonlywithapileofrequirements,it'soften__2__tomakesenseofwhattheauthorsoftherequirementsreallywantedthesystemtodo.Intheprecedingexample,usecasesreducetheambiguityoftherequirementsbyspecifyingexactlywhenandunderwhatconditionscertainbehavioroccurs;assuch,thesequenceofthebehaviorscanberegardedasarequirement.Usecasesareparticularlywellsuitedtocapturingthesekindofrequirements.Althoughthismaysoundsimple,thefactisthat__3__requirementcaptureapproaches,withtheiremphasisondeclarativerequirementsand"shall"statements,completelyfailtocapturethe__4__ofthesystem'sbehavior.Usecasesareasimpleyetpowerfulwaytoexpressthebehaviorofthesysteminwaythatallstakeholderscaneasilyunderstand.But,likeanything,usecasescomewiththeirownproblems,andasusefulastheyare,theycanbe__5__.Theresultissomethingthatisasbad,ifnotworse,thantheoriginalproblem.Thereinit'simportanttoutilizeusecaseseffectivelywithoutcreatingagreaterproblemthantheoneyoustartedwith. 3、____
A.modem
B.conventional
C.different
D.formal
正确答案是B