题目内容：

---- Is this school ___ your mother once warked for?
---Yes,she worked here for 30 years
A.where B.what C.the one D.that
为什么,请解析,

优质解答

这里C答案其实是省略了一个that,即Is this school the one that your mother once worked for?
由于这里school是作为worked for的宾语,因而引导词that可以省去.