The problem which ___at the meeting now is of great importance.

问题描述:

The problem which ___at the meeting now is of great importance.
A is discussing B being discussed C is being discussed D is to be discussed答案是C 为什么呢

有now ,表示正在进行,用现在进行时态
这个问题是被讨论,用被动语态
综合起来选C