語態(tài)有兩種：主動語態(tài)和被動語態(tài)。

　　主語是動作的發(fā)出者為主動語態(tài)；主語是動作的接受者為被動語態(tài)。
　1）若賓語補足語是不帶to 的不定式，變?yōu)楸粍诱Z態(tài)　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(tài)動詞+ be +過去分詞，構成被動語態(tài)。
　　 coal can be used to produce electricity for agriculture and industry.

let 的用法
　1）當let后只有一個單音節(jié)動詞，變被動語態(tài)時，可用不帶to 的不定式。
　　 they let the strange go.---> the strange was let go.
　
　2） 若let 后賓補較長時，let 通常不用被動語態(tài)，而用allow或permit 代替。
　　the nurse let me go to see my classmate in the hospital.
　　----> i was allowed / permitted to see my classmate in the hospital.

短語動詞的被動語態(tài)
　短語動詞是一個整體，不可丟掉后面的介詞或副詞。
　　this is a photo of the power station that has been set up in my hometown.
　　my sister will be taken care of by grandma.　　
　　such a thing has never been heard of before..

表示"據(jù)說"或"相信" 的詞組
　　believe, consider, declare, expect, feel , report, say, see, suppose, think, understand

it is said that…　　 據(jù)說　　
it is reported that… 據(jù)報道　　　
it is believed that…　大家相信　　　　　
it is hoped that…　大家希望
it is well known that… 眾所周知　　
it is thought that…　大家認為
it is suggested that…　據(jù)建議　　　　　
it is taken granted that…　 被視為當然　
it has been decided that… 大家決定　　
it must be remember that…務必記住的是

it is said that she will leave for wuhan on tuesday.