It做形式主語,代替由不定式,動名詞短語或是從句所表示的真正的主語.如It’s no use talking to him about it.
It做形式賓語,代替一個由不定式,動名詞,或是賓語從句,如I think it no use arguing with him.
it可以指季節(jié),時間, 距離
如 It wasmid summer.
It’s only five miles.
同時在強調(diào)句中,It + be + 要強調(diào)的部分+ that(who, whom) + 句子其他部分 .這個句型很重要,記住即可.
that有些固定的搭配 如 so that ,such that.
that 用作連詞,引導(dǎo)名詞性從句,狀語從句和強調(diào)句.
1. that名詞性從句.
①引導(dǎo)賓語從句.及物動詞后的引導(dǎo)詞that可省略.
I didn't expect (that) he could win the championship.
The teacher pointed out that Tom was not working hard enough.
② 引導(dǎo)主語從句.通常采用it作形式主語的句型.
That the earth goes around the sun is known to everyone.
（It is known to everyone that the earth goes around the sun.）
③引導(dǎo)表語從句.
The trouble is that we are short of money.
④引導(dǎo)同位語從句.
引導(dǎo)同位語從句的that和引導(dǎo)定語從句的that是不同的.前者只起語法作用,在從句中不作任何成分；而后者在定語從句中作主語、賓語或表語.舉例說明：
The news that he resigned from office surprised us.
The idea that he holds is very common nowadays on campus.
2. that引導(dǎo)狀語從句
①引導(dǎo)目的狀語從句.
Bring it nearer that I may see it better.
②引導(dǎo)結(jié)果狀語從句.
What have I done that he should be so angry with me?
③引導(dǎo)原因狀語從句.
I am afraid that I will fail in the driving test.
④引導(dǎo)讓步狀語從句.意為“雖然、盡管”.
Difficult that/as the task was, they managed to accomplish it on time.
⑤引導(dǎo)條件狀語從句.意為“假使、假設(shè)”.
Supposing that you were in my position, what would you do?
On condition that you were lost in the desert, you should ask for help as soon as possible.