单项选择题
Radar makes it possible for us（）in dense fog.
A.to be sailing B.sailing C.sail D.to sail
单项选择题 Raw la quer is（）corrosive nature.
单项选择题 Roll-on/roll-off ships are equipped with（）.
单项选择题 Shall we（）wait at the roadstead till there is a free berth for us?
