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过去完成时(Past Perfect Tense)表示在过去某个动作或某个具体时间之前已经发生或完成的动作或情况,表示句子中描述的动作发生在“过去的过去”。
Past Perfect Tense An action or circumstance that has occurred or been completed before an action or a specific time in the past indicates that the action described in the sentence occurred in “past tense ”.