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 Tom.
现在进行时:is/am/are being +done A new teaching building is being built in our school now.
过去进行时:was/were being +done A letter was being written by him at this time yesterday。