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
考查短语搭配。句中on board为“在飞机上”之意。句意：当飞机起飞和降落的时候，所有的乘客都要求系上安全带。