過去式的被動語態什麼時候用

當時態是一般過去時，語態是被動語態時，要用過去式的被動語態。

一般過去時的被動語態時構成是：

助動詞was/were+及物動詞的過去分詞

例句：

1、I sweep the floor yestetday.

→The floor was swept (by me) yestetday.

2、I bought a book last week.

→A book was bought (by me ) last week.

3、We visited their school yeaterday.

→Their school was visited (by us) yesterday.

主語是動作的接受者，一般為物，表達“某事被人做”，而且是過去被人做的時候，用過去式的被動語態。比如: The book was published last month. 這本書是上個月出版的。