单项选择题
Proper GMDSS watchkeeping includes（）.
A.monitoring all required frequencies in the proper mode B.reading all displays and/or printouts after silencing an alarm C.notifying the Master of any distress alerts D.All of the above
单项选择题 Our ship（）with many modern navigational instruments.
单项选择题 One method of reducing the length of radio transmissions without distorting the meaning of your words is by using（）.
单项选择题 On which vessels is GMDSS required? （）
