The problem( )last week is very important A was discussed B discussed C being discussed B
问题描述：
The problem( )last week is very important A was discussed B discussed C being discussed B
答
这个句子的谓语是后面的is，所以前面一定不能有was
discussed last week 是修饰The problem的定语，也是过去分词短语，因为表示上个星期发生过的事
答
过去分词做定语，因为是被动关系，所以是过去分词discussed
答
The problem (discussed) last week is very important 答案是 B. discussed 是因为句子实际上是The problem (which was) discussed last week is very important which was 是隐含的.
答
句子有谓语了 is（连系动词），就不能再用一个谓语动词（即有时态、语态变化的动词，如A）
过去分词表示被动以及已经完成的动作，两个都符合啊，问题被讨论、上周讨论的，因此用discussed