that 与what 的混用：
1.That they are going to discuss at the meeting is how to increase food supply in the world.(错误)
What they are going to discuss at the meeting is how to increase food supply in the world.(正确)
注：that在引导名词性从句时本身没有意义，也不在从句中充当任何成分；而what则表示“什么”“……的东西或事情”，在从句中充当主语，宾语或表语等。上句中的what 应充当discuss的宾语。

if 与whether的混用：
2.If we will visit the Great Wall tomorrow has not been decided yet.(错误)
Whether we will visit the Great Wall tomorrow has not been decided yet.(正确）
注：if 与whether 引导宾语从句时往往可换，但在下面情况时常使用whether：作介词的宾语时，见例①；在从句中提出两种选择时，见例②；从句提前时，见例③；引导主语从句，表语从句及同位语从句时，见例④。
①I worry about whether I hurt his feelings.
②She wasn’t sure whether she should laugh or cry.
③Whether he will come or not I don’t quite know.
④What many people are worried about is whether we will be able to build a better future.
We have some doubt whether they can complete the task on time.

that 与because 的混用:
3.(1)The reason why he was late for school was because he got up late.(错误)
The reason why he was late for school was that he got up late.(正确)
⑵Why farmland here is being lost is because farmers have cut down too many trees in recent years.(错误)
Why farmland here is being lost is because farmers have cut down too many trees in recent years.(正确)
注:reason作主语时引导的表语从句或why引导的名词性从句时常用that不用because.

忽略连词that:
4.These old languages are now threatened and may disappear is a serious matter to the people in Britain.(错误)
That these old languages are now threatened and may disappear is a serious matter to the people in Britain.(正确)
注：that在引导宾语从句时常常可省，但在下面情况时不可省去：宾语从句不止一个时，见例①；宾语从句与主句之间有插入语时，见例②；宾语从句为一个主从复合句时，见例③；引导主语从句，表语从句或同位语从句时，见例④。
①They complain (that) they have to work from morning till night, that it is hard to earn money, that they are bullied (欺负) by the policemen, or that the corporation leaders are seated lazily and enjoy the fruits of others’work.
②The teacher said, pleasantly and firmly , that we must overcome the difficulties.
③We believe that if we work harder, I will pass the National College Entrance Examination.
④The trouble is that she has lost his address.（表语从句)
Word came that China launched its first manned spaceship on Oct.15,2003.（同位语从句）

no matter who\what\which\how\where…与whoever\whatever\whichever\however\wherever…
5.No matter who breaks the rules will be punished.（错误)
Whoever breaks the rules will be punished.（正确)
注：whoever,whatever,whichever,however,wherever等连词可以引导名词性从句也可引导让步状语从句，而no matter who\what\which\how\where…只能引导让步状语从句。例如，
No matter how great the difficulty is, we ought to keep on.
Or: However great the difficulty is, we ought to keep on .

相似句型的混淆:
6.As is known to all that science plays an important part in the development of industry and agriculture.（错误)
As is known to all, science plays an important part in the development of industry and agriculture.（正确)
It is known to all that science plays an important part in the development of industry and agriculture.（正确)
注：as作为关系代词引导的非限制性定语从句位于主句之前时，从句与主句之间要用逗号隔开。It作为形式主语将that 引导的主语从句后置时，that常常不能省。