动词的语态有两种：主动语态和被动语态。

主语是动作的发出者为主动语态；主语是动作的接受者为被动语态。

1）若宾语补足语是不带to 的不定式，变为被动语态时，该不定式前要加"to"。此类动词为感官动词。具体包含：feel、hear、help、listen to、look at、make、observe、see、notice、watch。

例句：

The teacher made me go out of the classroom.

-> I was made to go out of the classroom （by the teacher）.

We saw him play football on the playground.

-> He was seen to play football on the playground.

2）情态动词+ be +过去分词，构成被动语态。

例句：

Coal can be used to produce electricity for agriculture and industry.