Not until then their marriage was breaking up because they had little in mon.
A. did I realize
B. I realized
C. had I realize
D. has I realized
网友回答
(答案→)A. did I realize
B. I realized
C. had I realize
D. has I realized
解析：考查倒装结构。否定词not until放在句首，主句的主谓要倒装，根据句意用一般过去时，选A。