What we used to think ws impossible now does seem possible.

What we used to think ws impossible now does seem possible.
What we used to think was impossible now does seem possible.语法正确吗?如何分析what在句子中的作用?

what we used to think was impossible now seems possible.这句话是what引导的主语从句.what we used to think was impossible在句中做主语,seem为谓语.而was并非多余,we used to think相当于插入语,你可以把它省略.句子就变成了what was impossible now seems possible.你如果去掉was句子就缺成分了不是嘛?主语从句中就没有谓语了,就不通了