where did you work?it was on the farm _that_ we worked.这里为什么

此题考查强调句型, 其结构为: It is/was+被强调部分+that+其他部分.

此题的问句是问:你在哪儿工作?( Where did you work?)
按照正常情况回答,应该是: I worked on the farm.(我在农场工作.)

这儿是用强调句型来回答的,对地点状语进行强调.故答句为:
It was on the farm that we worked .
on the farm是被强调部分. that是强调句型的引导词.

此题不能当作定语从句, 如当作定语从句,就必须用:
It was on the farm that we worked on.意思是: 在我们工作的农场.
(有点答非所问,不符合句意.故不是定从.)