Is she a teacher?--No,but she used to.此句后要be吗?

问题描述:

Is she a teacher?--No,but she used to.此句后要be吗?
这是一个对话.我不知道是用she used to be 还是she used to?

used to be 是个短语,意思是“过去是” 后面常加职业.
Is she a teacher?-- No,but she used to be(a teacher)回答中省略了这个