一道SAT 句子提升

问题描述:

一道SAT 句子提升
My father insists that before (buying a used car,have it )thoroughly inspected by a reputable mechanic.
A.
B.buying a used car,it is
C.buying a used car,I have it
为什么A错了,C是什么语法点?

饿 我刚做过这个题!就今天 a分句没有主语么,导致句意不清晰 (have it?让谁去修?不知道)所以选c