问题补充：
that you didn’t care about this matter at all, I should not have wasted my time explaining it to you.
A. Should I realize
B. Had I realized
C. If I realized
D. Did I realized
答案：
A. Should I realize
(答案→)B. Had I realized
C. If I realized
D. Did I realized
解析：考查条件中与过去事实相反的虚拟语气。其结构为if +主语+had done，主语+would /could/should/might + have done,省略if要倒装，had提前。故选B。
