单项选择题
A.The vessel moving upstream against the current
B.The vessel moving downstream with a following current
C.The vessel located more towards the channel centerline
D.The vessel with the least amount of maneuverability
单项选择题 A tug’s horsepower available at the shaft is（）.
单项选择题 A towing vessel should be on the crest of a wave at the same time as its tow and in the trough at the same time. The term used to describe this is（）.
单项选择题 A towboat has the same draft as the barges it is pushing ahead. If the distance from the stern of the towboat to the head of the tow is 260m，where is the approximate location of the pivot point of the unit?（）