you were brave enouh to disagree with what you boss said at the meeting but now,i regret__soyou were brave enouh to disagree with what you boss said at the meetingbut now,i regret__soa do b to do c doing d done

you were brave enouh to disagree with what you boss said at the meeting but now,i regret__so
you were brave enouh to disagree with what you boss said at the meeting
but now,i regret__so
a do b to do c doing d done

C
regret doing是指 后悔做过某事

B
为...抱歉,遗憾[+to-v][+that]
I regret to say that I am unable to help you.