Why not "n'a déjà mis la table"
déjà means "already", as in "I already set the table an hour ago".
why is sometimes mis la table ? and sometimes met la table ? HELP !
"Mis" is the past participle. "Avoir mis" is passé composé, a past tense. "Set the table" is in the past tense in this sentence. "Met" is third person, singular, present tense.