It was not until she failed in the exam she realized the importance of study.A. whenB. did

问题补充：

It was not until she failed in the exam she realized the importance of study.

A. when

B. did

C. and

D. that

答案：

A. when

B. did

C. and

(答案→)D. that

解析：

试题分析:句意：直到她考试失败了她才意识到学习的重要性。从结构判断此处是强调句型：it was ….that,而被强调部分是not until she failed in the exam，判断方法是去掉it was ….that部分，句子意思完整，故选D。