1.All these books need to be packed in to the boxes.
句里的need to be packed是need to be done的形式
主语是All these books所有的这些书需要被整理到盒子里去
2A.The teacher was already in the classroom when I arrived.
2B.She had already left when I phoned.
2A这个形式也是现在完成时.加上been 只是被动态.首先left不能"被'离开.其次因为left是短暂性动词,不可以加延续性的
3.他已经做完作业.以下翻译都对吗?
3a.He has finished his homework.
3b.He has done his homework.
正确的!