irresponsible
adj
(of people, actions, etc) not showing a proper sense of responsibility (指人、 行為等)不負責任的, 沒有責任感的
an irresponsible child 沒有責任感的孩子* irresponsible behaviour 不負責任的行為
It is irresponsible of you not to prepare students for their exams. 你不幫助學生準備考 試就是不負責. Cf 參看 responsible 4.