主語是動作的發出者為主動語態：主語是動作的接受者為被動語態。

　　1)　若賓語補足語是不帶to 的不定式，變為被動語態 時，該不定式前要加"to"。此類動詞為感官動詞。

　　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)　情態動詞+ be +過去分詞，構成被動語態。

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