3.名词性that从句中连词的省略问题

(1)当that从句作主语置于句首时，that不可省，但在口语中如果有形式主语it，that从句后置时，that可以省略。

It is surprising(that)he's made such rapid progress in his studies．

他的学习进步这么快，着实让人吃惊。

(2)that在引导宾语从句时，通常可以省略。

We know(that)sound can travel through air．

我们知道声音是在空气中传播的。

I am sure(that)he was wrong．

我敢说，他肯定是错了。

(3)在介词后的宾语从句中that常不可省略，且前面往往有个形式宾语it。

You may depend on it that they will support your plan．

他们会支持你的计划的，这个你放心。

See to it that you are not late again．

要保证再也不要迟到了。

(4)两个或两个以上宾语从句连用时，即使省略了第一个that，第二个和第三个that常常保留。

You can learn that the oldest person is a woman who lived to be 122 years and 164 days，that the longest moustache reached a length of 1.6 metres and that the longest poisonous snake is 5.71 metres long．(人教大纲版高三第3页)

你可以了解到寿命最长的人是个女人，活了122年164天;最长的胡须长达1.6米;最长的毒蛇有5.71米。

(5)当that从句与另一名词性从句并列作宾语时，that不可省略。

Everyone could see what was happening and that poor George was really frightened．

每个人都可以看到发生了什么，可怜的乔治真的很害怕。

(6)that从句独立出现，that不可省略。

—What did he say?—That he would never do it again．

——他说了什么?——他说他再也不会那样做了。

(7)当that从句为了强调放在句首时，that不可省略。

That poor George was really frightened，I can't believe．

我不相信可怜的乔治真的很害怕。

(8)当有插入语时，that不可省略。

Everybody could see，I believe，that George was really frightened．

我相信，大家都能看出乔治真的很害怕。

He said that，if he could managed it，he would come．

他说只要他能做到，他一定会来的。