listEning 3 "linguistiCsClAss" {$mEDiAurl} whAt ArE two kEy proBlEms For DEsCriptivE grAmmAr CliCk on 2 AnswEr ChoiCEs. A、thE inFormAtion is vEry CompliCAtED AnD suBjECt to ChAngE. B、thE FormAl lAnguAgE must BE EnForCED in All situAtions. C、thE lAnguAgE CAn BE orgAnizED CorrECtly in morE thAn onE wAy. D、thE DEsCription tAkEs timE BECAusE linguists must AgrEE.