◎ 题干
All passengers________are expected to fasten the seat belts when the plane takes off or lands.
[      ]
A. on the board  
B. on board
C. on boards  
D. on a board
◎ 答案
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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 passengers________are expected to fasten the seat belts when the plane takes off or lands.[ ]A. on the boardB. on boardC. on boardsD. on a board…”主要考查了你对  【介词和介词短语】  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。