I have been dreaming.That's why I didn't see.That's why可以用so来替换吗?That's why的原形,That's why是短语吗?

问题描述:

I have been dreaming.That's why I didn't see.That's why可以用so来替换吗?That's why的原形,
That's why是短语吗?

可以替换。。。都可以做因果关系的替代来补充上下文!

可以替换!
不算短语
但是固定一起用的很多 ...that is why...=.so.