为什么用“so……that”不用“such……that”

题目

为什么用“so……that”不用“such……that”
they are (so) busy studying (that) they can't play football with us.
多举些例子 类似的如何判断
为什么这个是 so+adj.+v-ing+that
这个so应该是修饰studying的，studying是动名词为什么不用such
如何判断是修饰busy还是studying的，有类似的吗？

答案

be busy doing sth 是一个固定搭配“忙于做某事”so+形容词/副词+that...; such+形容词+不可数名词/可数名词复数 +that ..； such+a/an +形容词+可数名词单数+ that...,e.g1) It is such an interesting book that I...