现在我们先试着翻译以下的句子： 

地球是圆的是众所周知的事。 

一种直接了当的翻译是： 

＊The earth is round is known to everyone.

 

遗憾的是，以上的句子是不对，我们必须加一个that到名词子句里去，以下的翻译是正确的： 

That the earth is round is known to everyone.

 

我们再来翻译一个中文句子： 

我要求他一定要用功念书。

 

直接了当的翻译可能像下面的： 

＊I demand he must work hard.

 

这是错的，我们应该加一个that在这个名词子句的前面。以下的翻译才是正确的： 

I demand that he must work hard.

 

虽然我们常看到这种that被省略的情形，我们仍希望大家知道，为保险起见，最好不要省掉that。以下是一些例子： 

That the sun rises from the west is wrong.（太阳从西方升起是错的） 

That a lot of Jews were killed during the Second World War is now a historical fact.（大批犹太人在第二次大战中被杀是历史上的事实） 

I didn't know that he is such a diligent student.（我不知道他是如此勤快的学生） 

I demand that you go away.（我要求你离开） 

I suggest that you go swimming every morning.（我建议你每天早上游泳） 

That we should all respect our parents should be taught to our kids.（我们该教孩子们尊敬父母） 

I don't think that he is a good athlete.（我不认为他是一个好运动员） 

Do you think that she is a good actress?（你认为她是一个好的演员吗？） 

That he can speak good English helps him.（他能说很好的文，这点对他很有帮助） 

I propose that we get married.（我建议我们结婚） 

Let us always remember that there are a lot of poor people in the world.（我们永远记住世界上有很多穷人） 

Never forget that we should always love one another.（不要忘记我们应该互相友爱） 

I am surprised to find out that he is a Catholic.（我很惊讶地发现他是个天主教徒） 

That we lost the game made all of us frustrated.（我们输了，这件事令我们大感沮丧） 

I can hardly believe that his English is so good.（我不能相信他的英文如此之好）