I failed in the job interview and only then the importance of learning English well.
A. I realized
B. I had realized
C. did I realize
D. had I realized
网友回答
A. I realized
B. I had realized
(答案→)C. did I realize
D. had I realized
解析：句意；我工作面试时失败了，直到那时我才意识到学英语的重要性。因为前面用failed，所以这里也用过去式。在and后的分句中，only then放在句首句子应用部分到装。故选C。