单项选择题
Any vessel shall，if the circumstances of the case admit，avoid（）in a narrow channel.
A.anchor B.to anchor C.anchoring D.to anchoring
单项选择题 An alternating light（）.
单项选择题 All persons or vessels within the lock area，including the lock approach channels，come under the authority of the（）.
单项选择题 A vessel which is being assisted by an icebreaker would display a flag hoist consisting of the code numeral 4 when the vessel（）.
