I was giving a talk to a large group of people, the same talk I to half a dozen other gr

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A. was giving
B. am giving
(答案→)C. had given
D. have given
解析：
此题提供的语境是：我当时正在给一群人作报告，这个报告我曾给其他若干批人讲过。由于was giving为过去进行时，而“曾给其他若干批人讲过”显然发生在was giving这一过去时间之前，故用过去完成时，即答案选C。