问题
选择题
Not until then _____ their marriage was breaking up because they had little in common.
A．did I realize
B．I realized
C．had I realize
D．has I realized
答案
答案：A
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。