单项选择题
（）by an ice-breaker, it is important to maintain a continuous listening watch on the appropriate VHF channel and to maintain a proper look-out for sound and visual signals.
A.which is assisted B.that assist you C.when you assisted D.when being assisting
单项选择题 The advantage of geostationary satellites is（）.
单项选择题 The frequency（）the safety message will be transmitted shall be included in DSC safety call.
单项选择题 We consider（）send a helicopter with medical facilities to the distress area.
