一道英语选择题,请问选哪个以及为什么

题目

一道英语选择题,请问选哪个以及为什么
the teacher____taught me when i was a child is___i am going to visit.
A.whom,where B.who,which C.who,the one D.that,which

答案

C
先行词是人,引导词作主语,故用who
第二空：特指那个老师 the one （who/whom )　　省略了引导词
加油!不明白再问!