关于主动语态改为被动语态的一些问题。

★ 注意：
1）感官动词主动语态的宾语补足语是不带to 的不定式，变为被动语态时，该不定式前要加"to"。例如：
The teacher made me go out of the classroom. 老师逼我走出教室。
--> I was made to go out of the classroom （by the teacher）.

We saw him play football on the playground. 我们看见他在草场踢球。
--> 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。例如：
Coal can be used to produce electricity for agriculture and industry.
煤可以产生工农业需要的电。

★ 特殊动词 let 的用法
1）当let后只有一个单音节动词，变被动语态时，可用不带to 的不定式。例如：
They let the strange go.他们放陌生人走了。
---> The strange was let go.

2）当let 后宾补较长时，let 通常不用被动语态，而用allow或permit 代替。例如：

The nurse let me go to see my classmate in the hospital.
那护士让我去探望住院的同学。
----> I was allowed / permitted to see my classmate in the hospital.

★ 短语动词的被动语态
短语动词是一个整体，不可丢掉后面的介词或副词。例如：
My sister will be taken care of by Grandma.
我妹妹由奶奶照顾。
Such a thing has never been hear