单项选择题
The approval period for a shipboard oil pollution emergency plan expires after （）.
A.one year B.two years C.four years D.five years
单项选择题 The Oil Record Book must be maintained onboard the vessel for （）.
单项选择题 Which of the following operations aboard a tanker must be recorded in the Oil Record Book（）.
单项选择题 For an upright vessel, draft is the vertical distance between the keel and the （）.
