单项选择题
A fairly accurate estimation of a ship’s position can be calculated by a technique known as（）.
A.dead reckoning B.Pilotage C.great circle sailing D.geographic navigation
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（）.
