初二被动语态

其实像这种时候可以先把句子换成陈述句：
如 Must i finish the homework
改为 i must finish the homework
被动 the homework must be finished by me
再改回疑问 must the homework be finished by me

如上，一下这句可
改为 you finish the homework
被动 the homework was finished by you
再改为疑问句 was the homework finishd by you

这样就会比较清楚了。以后遇到类似的句子都可以先这样处理，熟了就会懂。
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你问为什么不是
do the homework be finished by you?

我们先看这句 Do you finish the homework
它的肯定句是 you finish the homework ，变成上面的疑问句，因为没有be动词，就把do提出来做疑问词
但是do the homework be finished by you? 里面有do,又有be,当然是直接用be做疑问词就可以了，所以是错的。

do是助动词，在没有be动词而需要构成疑问句、否定句等的时候使用，当有be动词时，直接把be动词变作适当的形式使用就可以了，不用再加助动词

was 是系动词可以直接提前,不用do这个助动词了

Do you finish the homework?
Is the homeworkd finished by you?