was done是一般过去时，done这个过去分词在这里用做形容词，表示“一个事情完成了”这样一个状态。have done是现在完成时，had done是过去完成时。
双语例句
1、The work was done with the minimum amount of effort.
做这项工作没费什么劲。
2、The work was done according to her instructions.
这项工作是依照她的指示办的。
3、It was done without the principal's authority.
做这件事未经校长批准。
4、None of the work was done.
那些工作全都未干。
5、What beats me is how it was done so quickly.
使我困惑不解的是，这事怎么这么快就完成了。