单项选择题
A dead reckoning (DR) plot（）.
A.must utilize magnetic courses B.must take set and drift into account C.should be replotted hourly D.should be started each time the vessel's position is fixed
单项选择题 A dead reckoning (DR) plot（）.
单项选择题 A cardinal mark showing an uninterrupted quick-flashing white light indicates the deepest water in the area is on the（）.
单项选择题 A buoy，being a shape of cylinder and with red group flashing，shows that it is（）.
