THAT的“七不省”
That在英语中是一个使用频率很高的词。它可用作代词、连词、关系代词等，有时可以省略。但在以下几种情况下that不可省略，使用时尤其需注意。
一、that用作代词，指上文提到的人或事物(单数名词)，且需一个后置定语来修饰，此时that不可省
Their cotton output of1997 was double than that of1 987.
Mary’s handwriting is far better than that of Peter .
二、that用作连词，在so...that,such。。。that,in order thar等引导的状语从句中，that不可省。
They started so early that they might arrive in tim e.
It is such a heavy box that nobody can move it.
He worked hard in order that he might catch up with the others.
三、that用作连词，引导主语从句时，当它放在主句谓语动词之前时，that不可省。
That he came late made his teacher angry.
That she was chosen made us very happy.
如用it作形式主语，把从句置于谓语动词之后时，that可以省略。例如：
It is a pity(that) he has made such a mistake.
It is obvious(that) he is right.
四、that用作连词，引导表语从句和同位语从句时，that不可省。
The news that our team has won the match is true.
My idea is that we should get more comrades to do t he work.
五、that用作连词，引导宾语从句时，如主句的谓语动词是及物动词make,find,see等时，且后有宾语补足语时，that引导的从句可置于宾语补足语之后，用it作形式宾语，此时that不可省。
We find it necessary that he will succeed.
He made it clear that he was not interested in this subject.
六、that用作关系代词，引导定语从句时，当它作为从句的主语时，that不可省。
All that have to do is to practise every day.
That’s the same man that asked me for money yesterd ay.
但如that作从句的宾语时，that可省略。
The letter(that) I received was from my father.
七、在强调句型 It iswas...that结构中，that不可省。
It is English that Professor Li teaches us.
It was in Shanghai that I saw the film.