单项选择题
A.avoid crossing the channel at right angles
B.not overtake any vessels within the channel
C.keep as near as safe and practicable to the limit of the channel on her starboard side
D.when nearing a bend in the channel，sound a long blast of the whistle
单项选择题 A vessel is proceeding downstream in a narrow channel on the Western Rivers when another vessel is sighted moving upstream. Which vessel has the right of way? （）
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（）.