We( )the problem for quite some time,but we( )any conclusion yet. A.have been discussing.haven't reachedB.have disscussed.haven't been reaching C.discussed.haven't reachedD.had discussed.haven't reach
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简单做法：先看后一空：有yet,所以是have not done 即现在完成时+ 主动,（固定搭配：reach a conclusion）
第一空：由于后有提示还未结束,所以这个动作于过去开始,到了现在,将来还有可能继续,所以典型的have been doing即现在完成进行时结构
最后答案明确：A