问题描述：
改为被动语态
最佳答案： They built a new school last year.改为：A new school was built by them last year.被动语态的结构分类:一般现在时：be done（be随人称变化）一般过去时：was/were done一般将来时：will be done现在进行时：be being done（前面的be随人称变化，后面的being固定）过去进行时：was/were being done（being固定）将来进行时：will be being done（being固定）现在完成时：have/has been done过去完成时：had been done将来完成时：will have been done将来完成进行时：will have been done现在完成进行时：have been being done过去将来时：would be done过去将来完成时：would have been done过去完成进行时：had been being done过去将来进行时：would be being done过去将来完成进行时：would have been being done