这个that有什么用呀?

跟so ……that 差不多，如此……以致

sucu....that 如此....以至于

和文言文中一样缓解语气
THAT无实际含义

when I actually have a few free moments是状语
Racing the clock every day is such an exhausting effort that I tend to collapse（when I actually have a few free moments）
你应该这样看
such that 固定搭配

such ...... that .....引导原因状语从句
He is such a tall boy that he can reach the ceiling.
他是如此高的一个男生,可以够到天花板.

that的用法: 若先行词指人或物则代替先行词在定语从句中充当主语或宾语

The animal that \which is lost is a panda.

先行词 指物代替先行词在定语从句中充当主语

She is the person that \who we are worried about.

先行词 指人代替先行词在定语从句中充当宾语

另外，在题中，THAT引导的是一个定语从句,因为THAT 在句中做成分(应该是主语)不能省略,所以是定语从句.要是同位语从句的话,THAT在句中就不做成分了,仅仅是个连接词

注意1 that \which在代物时常常可以通用,但有时只宜于用which ,不用that

(1) 关系代词前有介词时.

This is the hotel in which you will stay.

(2) 如有两个定语从句,其中一句的关系代词是that,另一句宜于用which.

Let me show you the novel that I borrowed from the