语态有两种：主动语态和被动语态。主语是动作的发出者时为主动语态；主语是动作的接受者时为被动语态。
注意：
1）感官动词主动语态的宾语补足语是不带to 的不定式，变为被动语态时，该不定式前要加"to"。例如：
The teacher made me go out of the classroom. 老师逼我走出教室。
--> I was made to go out of the classroom （by the teacher）.
We saw him play football on the playground. 我们看见他在草场踢球。
--> 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。例如：
Coal can be used to produce electricity for agriculture and industry.
煤可以产生工农业需要的电。
