(06湖南24)I was giving a talk to a large group of people，the same talk I to half a dozen other groups.A. was givingB. am givingC. had givenD. have given

步骤 1：理解句子结构
句子的主干是“I was giving a talk to a large group of people”，其中“was giving”表示过去进行时，说明“我”在过去的某个时间点正在给一大群人做演讲。
步骤 2：分析从句
“the same talk I to half a dozen other groups”是定语从句，修饰“the same talk”。从句中缺少谓语动词，需要填入一个动词来表示“我”给其他六个组做报告的动作。
步骤 3：确定时态
由于主句使用了过去进行时，而从句的动作发生在主句动作之前，因此从句应该使用过去完成时，表示“我”在给一大群人做演讲之前已经给其他六个组做过报告。