如何判断that引导什么从句

that可以引导名词性从句、定语从句。that引导名词性从句时（即主语、宾语、表语、同位语从句），在从句中无具体含义，只起连接作用，而且在从句中也不作任何句子成分。

that可以引导以下从句

1、用作关系代词，引导定语从句 The only thing that I can do is to have a rest . 我唯一能做的事就是休息。

2、用作关联词，引导名词性从句

That the earth turns around the sun is known to all. 地球围着太阳转这一点是众所周知的。（引导主语从句）

It so happens that I know the man. 碰巧我认识那人。（主语从句）

I will see to it that everything is ready. 我会注意把一切准备妥当的。(宾语从句)

The trouble is that we are short of money.困难就在于我们缺钱。（表语从句）

There is no doubt that he is the best choice for this position. 无疑，他是这一职位的最佳人选。（同位语从句）

3、构成短语，引导状语从句

Bring it nearer so that I may see it better .拿近一点，好让我看清楚些。 ( so that 引导目的状语从句)

She got up early , so that she caught the early bus. 她起得早，所以赶上了早班车。( so that 引导结果状语从句)

In order that everybody should hear him , he spoke loudly. 他大声说话，为了使大家都能听得见。（in order that引导目的状语从句）

Now that they have taken matters into their hands the pace of events has quickened.他们既然已着手自己来处理问题，事态的进展也就加快了。（now that 引导原因状语从句）