四、被动语态

　　(一)被动语态的构成：be+过去分词

　　一般现在时 am / is / are +过去分词

　　一般过去时 was / were +过去分词

　　一般将来时 shall / will + be +过去分词

　　过去将来时 should / would + be +过去分词

　　现在进行时 am / is / are + being +过去分词

　　过去进行时 was / were + being +过去分词

　　现在完成时 have / has + been +过去分词

　　过去完成时 had been +过去分词

　　情态动词 情态动词+ be +过去分词

　　(二)被动语态的基本用法

　　当句子的主语和谓语呈被动关系，即主语是动作的承受者时(相对于执行者)，谓语要用被动语态。具体说来，被动语态主要用于以下两种情况：

　　1.不知道或没有必要说明动作的执行者。

　　Printing was introduced into Europe from China.

　　Such books are written for children.

　　Everything has been taken away.

　　When will the museum be opened for the public?

　　I was born in 1980.

　　2.动作的承受者是谈话的中心。

　　The composition was written with great care.