The robbery you saw last week wasn't a real one,was it?为什么要用was it you saw last week 在句子里是什么

问题描述:

The robbery you saw last week wasn't a real one,was it?
为什么要用was it
you saw last week 在句子里是什么

前句否定句,反问的时候就变肯定句.前句是wasn’t 反问用was
you saw last week是定语.
意思是你上周看到的抢劫不是真的吧?