◎ 题干
All flights   ___ because of the storm, they had to wait in the hall.
[      ]
A. have put off
B. were put off
C. have been put off
D. having been put off
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◎ 解析
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◎ 知识点
    根据n多题专家分析,试题“All flights___because of the storm, they had to wait in the hall. [ ]A. have put offB. were put offC. have been put offD. having been put off…”主要考查了你对  【现在完成时的被动语态】【独立主格结构】  等知识点的理解和应用能力。关于这些知识点的“档案”,你可以点击相应的链接进行查看和学习。