Y were brave enough to raise objections at the meeting.Well,now I regret ____that.

Y were brave enough to raise objections at the meeting.Well,now I regret ____that.
A to do B to be doing C to have done D having done
大虾们，能不能具体点呀 第一个句子是过去时，后面个句子又是现在时，里面再加个have done 过去分词之类的完成时,晕类！