We, a discussion with the teacher, came to understand the problem better.
A. holding
B. held
C. being held
D. having held
网友回答
A. holding
B. held
C. being held
(答案→)D. having held
解析：句意：跟老师讨论之后，我们终于对这个问题有了更好的理解。非谓语动词与句子主语存在逻辑上的主动关系，故排除备选项BC。显然“讨论”与“明白”时间上有先后，所以要用现在分词的完成式。