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。
feel,hear,help,listen to,look at,make,observe,see,notice,watch
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。
Coal can be used to produce electricity for agriculture and industry。