一、 当句子的主语是动作的执行者时，谓语的形式叫主动语态。当句子的主语是动作的承受者时，谓语的形式叫被动语态。被动语态由助动词be +过去分词构成，时态通过 be 表现出来。例如：

1 一般现在时：You are required to do this.
2 一般过去时：The window was broken by Xiao Ming.
3 一般将来时：The problem will be discussed tomorrow.
4 现在进行时：The road is being widened.
5 过去进行时：The new tool was being made.
6 现在完成时：The door has been painted.
7 过去完成时：He said that the work had been finished.
8 过去将来时：He said that the trees would be planted.

二、一些特殊的被动结构
1 、带情态动词的被动结构： 
The problem must be solved soon. 这个问题必须尽快解决。
2 、带不定式的被动结构：
Betty has never been heard to speak ill of others. 从未听到贝蒂说别人坏话。
This task needs to be done with great care.这项工作必须认真去做。

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