As ngonyama explains in his reply, some categories of verbs don't have passives, and as such only "hebben" is possible, or only "zijn" for the verbs that use "zijn" rather than "hebben". ###>As ngonyama explains in his reply, some categories of verbs don't have passives, and as such only "hebben" is possible, or only "zijn" for the verbs that use "zijn" rather than "hebben".