单项选择题
Radar is used to not only to look（）,but also to measure their distances away from you.
A.at obscured objects B.forward submerged targets C.up exposed targets D.for unseen objects
单项选择题 Radar makes it possible for us（）in dense fog.
单项选择题 Raw la quer is（）corrosive nature.
单项选择题 Roll-on/roll-off ships are equipped with（）.
