问题
选择题
All passengers _____ are expected to fasten the seat belts when the plane takes off and lands. [ ]
A. on aboard
B. on board
C. on the board
D. on boards
答案
答案：B
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All passengers _____ are expected to fasten the seat belts when the plane takes off and lands. [ ]
A. on aboard
B. on board
C. on the board
D. on boards
答案：B