A.连词：that, whether, if（这三个词都不作从句的成分，同时，that无含义，而whether和if都表“是否”）
B.疑问代词：who, whom, whose, what, which
C.疑问副词：when, where, why, how
①That the driver could not control his car was obvious.
②That she was chosen made us very happy.
③That he will come is certain.
④That he would take the risk is true.
⑤That he should have married her isn"t surprising.
①It was obvious that the driver could not control his car.
②It made us very happy that she was chosen.
③It is certain that he will come.
④It is true that he would take the risk.
⑤It isn"t surprising (that) he should have married her.
①Is it certain that he will come?
②Is it true that he would take the risk?
(1)It + be + 形容词+ that-从句
①It is likely that he will come.
②It is strange that she has ever trusted him.
③It is important that he (should) attend the meeting.
④It is best that he (should) go.
此句型在表示惊讶、喜悦、遗憾等感情色彩时，that从句中的谓语动词也常用 (should) + v原形。
It is strange that no one should have objected to the plan.
(2)It + be +名词+ that-从句
It is common knowledge that the whale is not a fish.
It"s a pity that he should have catched the train.
(3) It + be + -ed分词 + that从句
It is said that he is a famous writer.
It is reported that there will be a storm this afternoon.
It is suggested that the meeting (should) be held this afternoon.
It is demanded that he (should) leave at once.
(4) It + seem/happen/appear等不及物动词 + that从句。（look不接that从句，它接to be结构或形容词）
It seems that he is wrong.
It appears that they are in urgent need of help.
He looks (to be) surprised/happy/sad.
Whether he will win the game is not clear.
Whether he will come is uncertain.
Whether she comes or not doesn"t concern me.
It is not clear whether/if he will come.
It was uncertain whether he would come.
3. 连词代词what, who, which, whose等引导的主语从句。这些连接代词作用相当于代词，在从句中担当主语、宾语、表语、定语等。
What we need is more time.
Who was responsible for the accident is not yet clear.
Whose book it is not important.
Which school you want to go matters much.
4.连接副词when, where, why, how引导的主语从句。这些连接副词相当于副词，在从句中充当状语。
Why he did this is not known.
When he will come is still unknown.
It is not known why he did this.
How he succeeded is unknown to us.
Where we should hold the meeting needs to be discussed.
Whoever told you to give up smoking was quite right.
Whatever he gave you should be handed in.
Whoever told you that was lying.
Whoever comes is welcome.
1.______ makes mistakes must correct them.
A. What B. That C. Whoever D. Whatever
2. It worried her a bit ______ her hair was turning grey.
A. while B. that C. if D. for
3.When and why he came here ______ yet.
A. is not known B. are not known C. has not known D. have not known
4.______ is no reason for dismissing her.
A. Because she was a few minutes late B. Owing to a few minutes late
C. The fact that she was a few minutes late D. Being a few minutes late
5.______Tom liked to eat was different from ______.
A. That…that you had expected B. What …that you had expected
C. That…what you had expected D. What…what you had expected
6.______ we go swimming every day ______ us a lot of good.
A. If...do B. That...do C. If...does D. That...does
7.It ______ Bob drives badly.
A. thinks that B. is thought what C. thought that D. is thought that
8.It"s uncertain ______ the experiment is worth doing.
A. if B. that C. whether D. how
9.______ the boy didn"t take medicine made his mother angry.
A. That B. What C. How D. Which
10.______ we can"t get seems better than ______ we have.
A.What, what B. What, that C. That, that D. That, what
1.C 2.B 3.A 4.C 5.D 6.D 7.D 8.C 9.A 10.A