关于take it for granted要不要it的问题.牛津高阶英汉双解词典grant有一词组：take sth for granted,当它作为认为某事属实讲时,有个例句：I take it for granted you have read this book.我认为你一定读过这本书.这里you have read this book到底是不是个从句啊?就算是从句,且是同位语从句,就缺少that,我想到这个问题是因为有一道改错题,这样一句：We take it for granted the two most common forms of transmission——by means of sounds and by visual signs.这个句子应该把it去掉,后面的部分是宾语.但为什么上面那个句子就可以保留it呢?我知道这两个句子取自take sth for granted的两个不同的词义,但是英语句子在结构上还是可以类比的吧?

这个问题问的好，参考如下：
I take it for granted you have read this book.
这句话中it 是形式宾语，
you have read this book是真正的宾语，是个宾语从句，宾语从句前面的that可以省略。

We take for granted the two most common forms of transmission——by means of sounds and by visual signs.
这里的宾语是the two most common forms of transmission是个名词短语，不是从句，
所以不能用It做形式宾语.

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上面例子中的it是作形式宾语的，因为真正的宾语是一个句子，太长了。

可以类比.I take it for granted you have read this book.中it是形式宾语,真正的宾语从句就是：you have read this book(前面的引导词that省略了）.在We take it for granted the two most common forms of transmi...