That the earth moves around the sun is a truth.
Which team will win the match is a matter of public concern.
Where she has gone is not known yet.
What he does is none of your business.
That he will come is uncertain.
That we cannot undertake the task is a fact.
c) It引导的形式主语: 当主语从句较长时，多放在句子后部，用 it 作形式主语。
My idea is that we will go to the Great Wall on Sunday.
The truth is that I have never been there.
The fact is that we have lost the game.
That is why she was absent yesterday.
The house is where Lu Xun once lived.
1. ( ) the flight to New York will be delayed is ( ) I’m especially worried about.
A. If; what
B. Whether; that
C. When; that
D. Whether; what
2. Perhaps it will never be known ( ) he did with those materials on the incident.
【答案】B。it是形式主语, 真正的主语是后面的主语从句( ) he did with those materials on the incident。在这个主语从句中, what既是引导词也是动词did的宾语。固定搭配do with和what连用；deal with和how连用。
3. The Foreign Minister said, “( ) our hope that the two sides will work towards peace.”
A. This is
B. There is
C. That is
D. It is
【答案】D。前面用it作形式主语, 句中的that从句是名词性从句, 作真正的主语。外交部长说：“我们希望双方能相互合作, 致力于和平事业。”
4. ( ) surprised us most was that with all his money, he ( ) worry about a little thing like 5 cents.
A. It; could
B. What; could
C. What; should
D. It; should
【答案】C。第一空what引导主语从句, 并在从句中作主语。第二空情态动词should表示“竟然”之意, 是一种很惊讶的语气。句意：最让我们惊讶的是, 有那么多的钱, 他竟然担心5分钱这样的小东西。