主动语态：i eat apples .我吃苹果 .(主语发出动作)
被动语态：Apples are eaten by me .(不是主语发出动作，而是主语被做：动作的承受者)苹果被吃。
人们常说=事情被人们说：客观/符合英语的逻辑。
The dog eat a cake . 狗吃了蛋糕. ? 吃了那个蛋糕，蛋糕被谁吃了。(狗是主语/宾语是蛋糕)
适用范围：首先要有宾语：
①及物动词才有宾语
②不及物动词加介词（不及物动词不可以加宾语，但可以加介词就可以使用被动）
be + done 存在即合理 done :被动的动作(过去分词)be 表示被动的时间(各种的时态)和主语的单复数
Classrooms are cleaned (clean) every day .被动的动作：cleaned、被动的时间：现在、单复数：复数教室每天都打扫。
被动语态和时间相结合
一座新的大楼去年建造的。A new building was built (build) last year .
他每天被打。 He is beaten every day .
他昨天被打了。 He was beaten every day .
他明天将要被打。 He will be / is going to beaten every day .
他现在正在被打。 He is being beaten every day . 现在进行过时的被动：am/is/are + being done The classroom is being used .
他现在已经被打了。 He has been beaten every day . 现在完成时的被动：have /has + been done :现在的之前被… The work had been done .
eg: Our morning paper is read (read) by over 200,000 people every day .
eg : Last night my favorite TV program was interrupted (interrupt) by a special news bulletin 公告.
eg : His bike will be repaired (repaired) by his grandfather tomorrow .
eg : The new machine has been used (use) in our factory for two weeks .
与情态动词相结合：
Planes are heard .
Planes can/could/may/must be heard .(情态动词后面加动词原形)
这封信必须马上寄出。
The letter must be sent immediately .
天气不能被人们所控制。
Weather can not be controlled by people .