单项选择题
Shipboard Emergency Drills must be carried out at least（）on board cargo ship.
A.Once every third year B.Once a month C.Once a year D.Once a week
单项选择题 Full details of all lights and fog signals are shown on（）.
单项选择题 What is it called when it is possible to ignite the vapour above the oil?（）
单项选择题 Manoeuvring information can not be obtained from（）.
