单项选择题
Before entering an ice area，the ship should be（）.
A.either trimmed by the head or the stern B.on an even keel C.trimmed down by the head D.trimmed down by the stern
单项选择题 Any vessel shall，if the circumstances of the case admit，avoid（）in a narrow channel.
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（）.
