Anne's sister Margot was very upset that the family had to move为什么用that 提问

问题描述:

Anne's sister Margot was very upset that the family had to move
为什么用that 提问

因为that后引导的是一个表语从句。

Anne 的姐妹 Margot 因要搬家而感到不愉快/苦恼

be + adj.+ that从句
从句用以补充解释形容词,以此举为例,Margot之所以感到upset,是因为the family had to move.