时间：2022-09-10 12:48:14
名词性从句可以分为主语从句、宾语从句、表语从句和同位语从句四种，在选用引导词时，what和that极易被混淆，让我们从用法上来看看两者的区别。
（1） what在从句中担任句子成分，that不担任
what在引导名词性从句时往往在从句中担任一定成分，表示疑问、感叹或指代“所……的人/事物”；而that引导名词性从句时仅作引导词，无意义，所以它引导的从句本身必定是完整的。例如：
主语从句What Mary is is a secret. （what表示疑问）That he finished the work in such a short time surprised us all.
宾语从句I don’t know what a naughty boy he is. （what表示感叹）He said that he would go to the college the next year.
表语从句This book is what I want to tell you about. （what相当于the one that）The fact is that he has not been seen recently.
同位语从句They have no idea at all what he is working on. （what表示疑问）Word came that their team had won the championship.
（2） what在任何从句中都不能省略，that引导宾语从句时有时可以省略
由于what在其引导的从句中担任一定的句子成分，所以任何时候都不能省略；而that在名词性从句中只起引导作用，不担任句子成分，在宾语从句中有时可以省略，但在其他三种名词性从句中不能省略。
例如，What she told me is not true一句中，what在主语从句中作told的宾语，不能省略，也不能用that代替，否则句子不完整；John said (that) he was leaving for London on Wednesday一句中，宾语从句句意完整，故用that，且that可省略。
但在以下几种情况中，宾语从句中的that不能省略。
■当宾语从句被分隔时。如I don’t doubt, in any case, that he keeps his word一句中，从句被短语in any case分隔，that不能省略。
■当宾语从句本身为复合句时。如He told me that if he was free he would drive me there一句中，从句if he was free he would drive me there本身为复合句，that不能省略。
■当宾语从句的主语为that时。如The man said that that was really an adventure to him一句中，从句的主语为that，为避免混淆，引导词that不能省略。
■当有并列的宾语从句时。如Everyone could see what was happening and that poor Tom was nearly frightened一句中，动词see的宾语是由and连接的、分别用what和that引导的两个并列的从句，that不能省略。如果省略that，整个句子就会成为由and连接的并列句，句意与原句不同。
（3） that引导的主语从句可以后置，what引导的主语从句中只有表示疑问含义的可以后置
主语从句位于句首会使句子显得“头重脚轻”，因此常把它移到句子的尾部，前面用it作形式主语。这在that引导的主语从句中最常见，如：
It is clear to anyone with eyes that the animal looks like a wall. = That the animal looks like a wall is clear to anyone with eyes.
很多时候，It is...that...已成为一种惯用句型，如It is a pity that..., It is strange that...等。但要注意，像It is more time that we need这样的句子是It is...that...构成的强调句型，不可与主语从句后置相混淆。
而what只有引导表疑问含义的主语从句时，才可以用it作形式主语，将从句后置，如：
It is not yet decided what will be done next. = What will be done next is not yet decided.
（4） what引导的从句可以作介词的宾语，that引导的从句只能作部分介词的宾语
what引导的从句用作介词的宾语很常见，例如：With his camera, he kept taking pictures of what he did and saw.
但只有少数几个介词，如except, but, in后面可以直接跟that引导的宾语从句，其他介词后面须加it作形式宾语，才可以接that引导的宾语从句。例如：
The two brothers are similar in that they both like sports.
The room is comfortable to live in except that the furniture are a bit too old.
You can depend on it that he’ll try his best to help us.（it是形式宾语）
（5） what引导的从句可以作宾语补足语，that引导的从句不可以
what引导的名词性从句可以充当宾语补足语，而that引导的则不行。例如：We will make the factory twice what it is today（我们将把工厂扩大到今天的两倍）一句中，twice what it is today是宾语the factory的补足语。
【牛刀小试】
1.fashion differs from country to country may reflect certain cultural differences.
A. What B. That C. This D. Which
2. It is not yet pretty well understoodmakes the rainforest disappear year by year.
A. that B. when C. what D. how
3.impressed me most wassuch a little boy could play the violin so well.
A. That; what B. What; that C. That; that D. What; what
4. Great changes have taken place in that school. It is no longerit was 20 years ago.
A. what B. that C. how D. which
5. The reason why he was late washe had taken a wrong bus.
A. because B. whether C. what D. that
6. Little Tommy was reluctant to tell the headmasterhe had done the day before.
A. that B. how C. where D. what
7. He told uswhen he was young, he decided to travel around the world.
A. that B. what C. if D. /
8. Please see to itthere are enough seats for all of the guests.
A. what B. which C. that D. where
9. I have another question _____ we shall do next.
A. that B. what C. if D. this
10. It was what you do rather thanyou saymatters.
A. that; what B. what; what C. that; that D. what; that
【参考答案】
1. B （主语从句，句意已完整，用that引导）
2. C （主语从句，动词makes需要主语，用what引导）
3. B （主语从句中，动词impressed需要能担任主语的引导词，故用what引导；was后的表语从句不缺成分，故用that引导）
4. A （后半句是一个表语从句，what作从句中的表语，意为the school that）
5. D （引导一个句意完整的表语从句，用that）
6. D （从句中的动词had done需要宾语，故用what）
7. A （宾语从句本身为复合句，因此引导词that不能省略）
8. C （介词to后须先用形式宾语it，才能跟that引导的宾语从句）
9. B （what引导同位语从句，且在从句中作谓语动词do的宾语）
10. D （It was... that matters是一个强调句型，所以第二空选that；被强调的是动词matters的主语从句，what在主语从句中作动词say的宾语）
KEYs to The House of 1,000 Mirrors:
①of ②lifted ③wagging ④his ⑤who
⑥and ⑦to see ⑧to ⑨never ⑩faces
All the faces in the world are mirrors. Others’ reflections depend on you yourself.