It’s said that… that引导的从句在句中作_______(成分)

It’s said that… that引导的从句在句中作_______(成分)
It’s said that… that引导的从句在句中作_______(成分)

It’s said that… that引导的从句在句中作_______(成分)
是主语,因为引导的是主语从句
参考：
主语从句
定义:在句子中担当主语的是一个从句,这个从句就叫做主语从句.
主语从句是在复合句中充当主语的从句,通常放在主句谓语动词之前或由形式主语it代替,而本身放在句子末尾.
1、主语从句常用it作形式主语,一般常用句型为：
It is+{名词/形容词/过去分词}+主语从句例如：
It is still a question whether she will come or not.
It is strange that you should like him.
It is still unknown which team will win the match.
另外,还有一些比较多见的结构：
It turned out that……；
It has been proved that……;
It happened/occurred that……；
It is well-known that……等等
2.用it 作形式主语的结构
(1) It is +名词+that从句
It is a fact that … 事实是…
It is an honor that …非常荣幸
It is common knowledge that …是常识
(2) it is +形容词+that从句
It is natural that… 很自然…
It is strange that… 奇怪的是…
(3) it +不及物动词+that从句
It seems that… 似乎…
It happened that… 碰巧…
(4) it is+过去分词+that从句
It is reported that… 据报道…
It has been proved that… 已证实…
3.主语从句不可位于句首的五种情况
(1) if 引导的主语从句不可居于复合句句首.
(2) It is said ,(reported) …结构中的主语从句不可提前.
例如：　　It is said that President Jingo will visit our school next week.
(3) It happens…,It occurs… 结构中的主语从句不可提前.
例如：　　It occurred to him that he failed in the examination.
(4) It doesn’t matter how/whether …结构中的主语从句不可提前.
例如：　　It doesn’t matter whether he is wrong or not.
(5) 含主语从句的复合句是疑问句时,主语从句不可提前.
例如：　　Is it likely that it will rain in the evening?
其中(4) it is+过去分词+that从句
It is reported that… 据报道…
It has been proved that… 已证实… 　这里就是
和(2) It is said ,(reported) …结构中的主语从句不可提前.
例如：　　It is said that President Jingo will visit our school next week.
要注意区别 宾语从句是说that成分整个在句子中作宾语 而这个that做主语的
以上来自百度名片

做主语
因为it's只是形式主语，他后面的从句或者是不定动词才是真正的主语。
这是八年级的重要知识。