“had done” 是过去完成时态。在英语中,过去完成时用于表示在过去的某个时间点之前已经发生或完成的动作。它通常由助动词 “had” 加上动词的过去分词构成。
以下是一些应用情境:
完成的动作在过去某时之前发生:
例句:By the time I arrived, they had already eaten dinner.(当我到达时,他们已经吃过晚饭了。)
过去某时之前的持续动作:
例句:She had lived in that city for five years before moving to a new one.(在搬到新城市之前,她在那座城市住了五年。)
过去某时之前的完成状态:
例句:He realized he had left his keys at home after reaching the office.(他在到达办公室后意识到他把钥匙落在家里了。)
表示过去的条件情况:
例句:If I had known about the traffic, I would have taken a different route.(如果我当时知道交通情况,我就会选择不同的路线。)
总体而言,“had done”是过去完成时态,用于强调过去某个时间点之前已经完成的动作或状态。