She failed in the exam, ( ) proves that she wasn't working har

She failed in the exam, ( ) proves that she wasn't working hard engough at school.
A、this
B、it
C、that
D、which
【正确答案】：D
【题目解析】：which 引导定语从句且which指代为前半句，句子含义是她考试没有通过，事实证明她在学校学习不够努力。