谁能告诉我用最简洁明白的话把主语从句的语法讲明白了呢?

谁能告诉我用最简洁明白的话把主语从句的语法讲明白了呢?

定义
　　在复合句中充当主语成分的句子叫做主语从句.
第一部分
　　常规主语从句,即句子在复合句中充当一个主语 　　主语从句的时态：不受主句的时态影响和限制.　　（1）That he finished writing the composition in such a short time surprised us all.　　（2）Whether we will go for an outing tomorrow remains unknown.　　（3）Who will be our monitor hasn't been decided yet.　　（4） Whom we must study for is a question of great importance.　　（5）What caused the accident remains unknown.　　（6）Whatever you did is right.　　（7）Who the watch belongs to was lost is unknown.　　（8）What we need is time.　　（9）What we need are good doctors.　　小结:　　（1)引导主语从句连词有that,whether,who,what,whatever等 　　（2)连词位于句首不能省略 　　（3)主语从句大多数情况下视为第三人称单数,但也有例外,如例（9）
第二部分
　　为了防止句子头重脚轻,通常把形式主语it放在主语位置,真正主语搁置于句末 　　（1）It is certain that he will win the match.　　（2）It is true that he has made a very important discovery in chemistry.　　（3）It is very likely that they will hold a meeting.　　（4）It is strange that he should do that.　　（5）It is important that we all should attend the meeting.　　（6）It is strange that the man should have stuck to his silly ideas.　　（7）It is a pity that we won't be able to go to the south to spend our summer vacation.　　（8）It is still a mystery what caused the accident.　　（9）It is said that he has gone to shanghai.(=He is said to have gone to shanghai) 　　（10）It is known to all that the gun powder was first invented by the Chinese.　　（11）It is suggested that the work should be done with great care.　　（12）It seems that he has seen the film.(=He seems to have seen the film) 　　（13）It happened that the two cheats were there.(=The two cheats happened to be there) 　　小结:　　（1)以that 引出的主语从句,常以形式主语it引导.It is +形容词/名词/某些动词ed + that 从句.　　（2) 在有些that从句中要用虚拟语气 (should+do/should+have done)例句4,5,6,11.