求助 GMAT时态的一题

Vicky0722

曼哈顿problem set中一题
Last Monday mary realized that she would have to spend all of that night rewriting her application because she did not back up her files.
这里答案是把did not back up 改为had not backed up. 请问为何这里用的是过去完成时？

emmahiggins09

没有做back up 的这个动作是发生再realised 和 would have to 之前的, 过去的过去便是过去完成时态了

楼主可以画条时间轴直线来看清 sequence

Vicky0722

emmahiggins09 发表于 2017-1-25 20:25
没有做back up 的这个动作是发生再realised 和 would have to 之前的, 过去的过去便是过去完成时态了

楼主 ...

懂了谢谢！