定语从句的引导词能做表语的不只有that which为什么也可以?如下题

Atfer 10 years of hard time,the young lady has turned movie star,（ ） she dreamed of becoming in her childhood .
A who B which C that D what
首先,这是一句非限制性定语从句,只能用which或者as引导的,不能用that引导的
as意思为作为,这边解释不通,所以只能选which,which指代的是后面整件事