高中英语 这里的that什么意思？

典型的that从句
that名词性从句。
①引导宾语从句。及物动词后的引导词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 引导主语从句。通常采用it作形式主语的句型。
That the earth goes around the sun is known to everyone.
（It is known to everyone that the earth goes around the sun.）
③引导表语从句。
The trouble is that we are short of money.
④引导同位语从句。
引导同位语从句的that和引导定语从句的that是不同的。前者只起语法作用，在从句中不作任何成分；而后者在定语从句中作主语、宾语或表语。举例说明：
The news that he resigned from office surprised us.
The idea that he holds is very common nowadays on campus.

这是表语从句的先行词，没有实际意思。请及时采纳哦

That在其中作为引导主语从句的标志，可以不用翻译。主语是吸血鬼的弱点，后面加that引起注意，有起到解释说明的作用。