在之前的内容里，我们已经学习了名词性从句中的宾语从句和表语从句啦，今天继续来学习主语从句。
顾名思义我都懒得说了，就是主语由一个句子来充当。你看，其实名词性从句就这么点儿刷子~
你们看到啦，主语由that引导的句子充当，而谓语部分往往又很短，显得句子头重脚轻，一点儿都不好看，怎么办嘞？这个时候就用到万能的it了～我们把it放到主语从句的位置，而把真正的主语置于句尾，就变成酱紫：
It is known to all that knowledge comes from practice.
嗯，顺眼多了～
这种比较常见的结构并不难总结，概括如下：（写作经典句式，别说我没告诉你！）
1.It is +adj.+主语从句
常见句式：
It is obvious/evident/apparent that…显然…
It is indisputable that…无可争议的是…
It is undeniable that…不可否认的是…
It is possible/likely that…可能…
Eg：It is indisputable that air pollution is an extremely serious problem.无可争议，空气污染是个极其严重的问题。
2. It is +done（过去分词）+主语从句
常见句式：
It isreported that…据报道…
It is widely/generally/commonly acknowledged/thought/considered that…人们普遍认为…
Eg: It is generally acknowledged that technology makes modern life more convenient.人们普遍认为科技使现代生活更便捷。
3. It is + n. +主语从句
常见句式：
It is common knowledge that···是常识
It is a miracle that···真是奇迹
It is an essential fact that···事实证明
Eg：It is common knowledge thatto cooperateis the very nature of human being from the very beginning.合作正是人类最初的本质，这是常识。
Well，最后的最后，依然是practice time：（答案见明天的首条评论噢）
1.他是什么时候出国的没有人知道。
2.你喜欢的不管哪个玩具都是你的了。
3.她是怎么做到连续工作48小时的让人很感兴趣。
4.我们中间不论谁首先完成了任务应该去帮助其他同学。
网友评论
1. When he goes abroad is not known.
2. Whichever toy you like is yours.
3. How she can work 48 hours continuously interests us.
4. Whoever finishes the mission should help others among us.