单项选择题
Vessel towing with the current shall（）tow more than two boats and they must be towed alongside.
A.at times B.at any time C.at no time D.at moment
单项选择题 Vessels are required to illuminate their（）to aid identification.
单项选择题 Vessels ramaining（）a few hours should moor with anchors.
单项选择题 Vessels should be manned（）duly qualified officers and crew adequate（）ensure the safety of navigation.
