{$mEDiAurl} why DoEs thE proFEssor sAy this:
A、to inDiCAtE thAt stuDEnts shoulD AlrEADy unDErstAnD thEsE DiFFErEnCEs.
B、to notiFy stuDEnts thAt it is not EssEntiAl to mEmorizE this inFormAtion.
C、to imply thAt thE DistinCtion BEtwEEn thE two usAgEs is ovErstAtE
D、
D、to EmphAsizE thAt hE DoEs not hAvE timE to DEFinE tErms usED in thE tAlk.