All passengers________are expected to fa
问题:
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
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