It was not until she failed in the exam she realized the importance of study.
A. when
B. did
C. and
D. that
网友回答
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。