She found her calculator-----she lost it.

She found her calculator_____she lost it.
A where.B when C in which D that
劳烦诸位解答,在下感激不尽.

答案是A：where
首先说为什么不是C：in which, 因为理论上in which可以替代WHERe,但是就这个句子来看,你可以注意下 in calculator是不成立的,因为calculator不是一个地点词,不是类似PLACE这样一类的词汇.我举个例子给你,
he found his calculator in the place ,in which he lost it..这句里的in which可以和where通用,引导定语从句.
再说为什么不是D：that
如果用THAT, 那么句子应该是She found her calculator that she lost.注意这里的定语从句里不应再包含it了.that引导定语从句.
再次,说说为什么不是WHEN.
WHEN从语法上讲得通,但从意思上讲不通.丢的时候找到了,怎么可能呢?
我再举个WHEN的用法,
作状语用,SHE FOUND HER CALCULATOR WHEN SHE WAS CHECKING HER DRAWER.
因此答案里的where就好像when作状语作为地点状语使用.
建议：多研习一下定语从句中when和where的用法,区分好它们在引导定语从句时和做状语从句时区别.