一般现在时:is/am/are +done The classroom is cleaned （by the students) every day.一般过去时:was/were +done 300 trees was planted last year.现在完成时:has/have been +done The work has been finished by ...中文有木有1.教室每天被打扫。2.去年种了300棵树。3.这项工作已经被汤姆完成了。4.现在我们学校正在建设一座新的教学楼。5.昨天这个时候，他正在写一封信。我也是临时想的，希望能帮上你。