单项选择题
A tug is best positioned for towing and maneuvering on rivers and other restricted waters where wave action is limited when（）.
A.directly astern and pushing the tow B.towing on a hawser C.towing alongside and parallel to the vessel it is towing D.towing on the hip
单项选择题 A tug is “in irons” when held in a fixed position by（）
单项选择题 A tug in irons is（）.
单项选择题 A tsunami is caused by a(n)（）.
