1.動名詞和不定式作主語
v-ing通常表示已知的事實或曾經(jīng)做事
to do通常表示一種意愿、目的或未完成的事
注意：不定式或動名詞做主語時往往會形成主語太長的現(xiàn)象故通常用代詞it
例如：Collecting stamps is one of his hobbies.
It's one of his hobbies to collect stamps
It 是形式主語 collect stamps 是真正主語
2.名詞性從句作主句
（1）That從句
That he doesn't study makes me angry.
It makes me angry that he doesn't study.
（2）Whether從句
從句可用ye/no回答的問句變化而成，這種可用yes/no回答的問句稱為一般疑問句。
a.問句有be動詞或一般助動詞（can,will,may,should,ought to）
例如：Has he done It?
Whether he has done it?
b.問句有do,does,did等助動詞時
例如：Did he come?
Whether he come?
（3）疑問詞引導(dǎo)的從句（when,what,how,where,why）
a.問句有be動詞時
what is he doing?
what he is doing
b.問句有一般助動詞時
where can he find it?
where he can find it.
c.問句有do,does,did等助動詞時
what did he write?
what he wrote.
注意：who,what,which為疑問代詞時
①who came here
②what happened
③which was bought
變?yōu)槊~性從句時，結(jié)構(gòu)不變
3.名詞性短語作主語
（1）疑問副詞
a.where to live
b.when to talk to him
c.where to try again
d.how to do It
（2）疑問代詞
a.what to do
b.which to buy
c.whom to see
d.whom to talk to
4.表示距離的地點副詞短語作主語? ? ? （from..... to......）
例如：From Shanghai to Beijing is about 1000 kilometers.
It's about 1000 kilometers from Shanghai to Beijing.
