(1)从属连词that。如：That they were in truth sisters was clear from the facial resemblance between them.
Whether he’ll come here isn’t clear.他是否会来这里还不清楚。
What she did is not yet known.她干了什么尚不清楚。
How this happened is not clear to anyone.这事怎样发生的，谁也不清楚。
Whoever comes is welcome.不论谁来都欢迎。
Wherever you are is my home----my only home.你所在的任何地方就是我的家----我唯一的家。
It is certain that she will do well in her exam.毫无疑问她考试成绩会很好。
It is probable that he told her everything.很可能他把一切都告诉她了。
B.It+be+名词词组(no wonder,an honour,a good thing,a pity,no surprise,etc.)+that从句。如：
It’s a pity that we can’t go.很遗憾我们不能去。
It’s no surprise that our team should have won the game.我们没赢这场比赛真意外。
It is said that Mr.Green has arrived in Beijing.据说格林先生已经到了北京。
It is reported that China has sent another man-made earth satellite into orbit.
It seems that Alice is not coming to the party at all.Alice似乎不来参加晚会。
It happened that I was out that day.碰巧我那天外出了。
E.It+doesn’t matter(makes no difference,etc.)+连接代词或连接副词引起的主语从句。如：
It doesn’t matter whether she will come or not.她是否来这无关紧要。
It makes no difference where we shall have the meeting.我们在哪里开会毫无区别。
Is it true that the scientist will give us a lecture next week?下周那位科学家将给我们作报告是真的吗?
Does it matter much that they will not come tomorrow?他们明天不来很要紧吗?
How strange it is that the children are so quiet!孩子们这么安静真奇怪!
Whoever comes will be welcome.(whoever=the person who)来的人将受到欢迎。
Whatever he did was right.(whatever=the thing that)他所做的事情是正确的。
Whichever of you comes in will receive a prize.(whichever=anyone of you who)你们当中不论哪个进来将会得到奖