I can’t thank you too much for your kindness because without your help Ihave won the first

I can’t thank you too much for your kindness because without your help I have won the first prize in the speech contest．
A. can’t
B. shouldn’t
C. might not
D. couldn’t

A. can’t B. shouldn’t C. might not (答案→)D. couldn’t解析：考查情态动词的虚拟语气的用法。意为，我再感谢你也不为过，没有你的帮助，我不可能在演讲比赛中获得第一名。根据句意可知，演讲比赛已经结束。Can't have done 不可能做了某事。 Shouldn't have done 本不应当做某事 might not have done 可能没有干某事，均不符合题意。

我也是这个答案