Question

英语语法问题！？！

what the chemical process is that's causing it.
表语从句中that不是不做成分吗，那后面that's causing it.里面的that为什么作主语？是因为它省略了一个that吗 what the chemical process is（that） that's causing it.？？？

Answer 1

是的，省略了一个that，但这个that没有实际的含义，可以省略。