一句从句问题

It是形式主语，真正的主语是to guess what her reaction to the news could be.这个不定式结构。这不是主语从句。比如，It is difficult to work out the problem.
what her reaction to the news could be.
是个宾语从句，做guess的宾语。
我说的是对的，因为我唱给学生将这个。

It是形式主语，真正的主语是what her reaction to the news could be

改写成what her reaction to the news could be was difficult to guess.

只是一个结构，不是从句

我认为这是一个双重从句：主语从句+宾语从句
主语从句：to 后边的整体看是主语从句
宾语从句：what引导的是宾语从句

这个句子可以改为：What her reaction to the news could be is difficult to guess.我也认为是主语从句，但是不是因为它是it开头，而是此复合句的主语What her reaction to the news could be是个小句子。

i在此句中叫做形式主语，代指后面的to do 或者that从句。这句guess后面what引导的是宾语从句。真正的主语是to guess what.......
再举一例你就明白了。It is necessary that we should learn English.正常语序应该是that we should learn English is necessary.但这样写使句子看起来啰嗦。有头重脚轻的感觉所以用it 代指that从句。

1. it=to guess what her reaction to the news could be。

2. what her reaction to the news could be是宾语从句，是guess的宾语。

3. 为了看清楚语法，还原成：To gu