发布时间：2016-04-27 来源：新东方在线 发布人：zolo
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.