单项选择题 （）should ensure that adequate measures are taken to prevent alcohol and drugs from impairing the ability of watchkeeping personnel.

单项选择题 You are about to cross a narrow channel when you see an approaching vessel that can only be navigated safely within the channel.You should（）.

单项选择题 Between April and November, squalls（）as Sumateras（）in Malacca Strait in the late afternoon or overnight and（）E to affect the W coast of Malaysia and Singapore Island.