4、名词性从句做主语。
首先得弄清楚什么是名词性从句？它起什么作用？
定义：在句子中起名词作用的句子叫名词性从句(Noun Clauses）。
我们都知道在英语中名词可以作主语、宾语、同位语、表语 、定语、状语、补语。
因此根据在句中不同的语法功能名词性从句可分为：
A.主语从句（作主语）：That the earth is round is true.
B.宾语从句（作宾语）：Do you know where he lives.
C.表语从句（作表语）：My opinion is that you should not go alone.
D.同位语从句(于解释说明前面的名词)：
The fact that the earth is round is true.
根据构成来看名词性从句一共有三种：
（1） That从句。任何一个主语起首的句子前加That就是that从句。
例.That the earth is round is true.
（2）Whether 从句。
Whether从句由可用yes或no回答的一般疑问句变化而成，具体分为：
A. 问句有be动词和助动词（can、will、may、should、ought to、have、must）时。主语与be动词或助动词还原，前面加上whether，这就形成了whether从句。
例1.Is he happy?→ whether he is happy.
I don’t know whether he is happy. Whether从句在复合句中作宾语
例2.can he do it? →whether he can do it.
Whether he can do it is still unknown.Whether从句在复合句中作主语。
B. 问句有do、does、did等助动词时。主语与助动词还原，再将助动词Do、does、did去掉，后面的动词依人称和时态变化。
例1. Did he come? →whether he did come → whether he came.
例2. Does he like it? →whether he likes it
（3）疑问词所引导的从句。
由疑问词（when、what、how、where、why）等特殊疑问句变化而成。具体分为：
A. 问句有be动词和助动词时。主语与be动词或者助动词还原，前面保留疑问词。
例1. What are you doing? → what you are doing
I want to know what you are doing.在复合句中作宾语
例2. Where can he find it? → where he can find it.
Where he can find it is unknown. 在复合句中作主语
B. 问句有do、does、did等助动词时。主语与助动词还原，前面保留疑问词；再将助动词Do、does、did去掉，后面的动词依人称和时态变化。
例1. what did he write? → what he wrote.
注意：Who、what、which为疑问代词，若在句中作主语，变成名词性从句时结构不变。
例1. who came here.
例2. What happened last night.
例3. Which was bought.
5、名词短语作主语
名词短语由“疑问词 ＋ 不定式短语”形成
① 疑问副词
Where to live
Whether to try again
When to talk to him
How to do it
例1. Where to live is still unknown.
例2. Whether to try again is still not decided
② 疑问代词
What to do
Whom to see
Which to by
例.which to buy depends on how much money do you have.
6、表距离的地点副词短语做主语
From + 地点 + to + 地点
例.from shanghai to Beijing is about 1000 kilometers.
如果主语太长可以用it代替做形式主语。
这期就到这里，我们下期再见！