A fairly accurate estimation of a ship’s position can be calculated by a technique known as（）.

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（）.

A.ignores the effect of surface currents
B.is most useful when in sight of land
C.must be plotted using magnetic courses
D.may be started at an assumed position

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（）.

A.north side of the mark
B.west side of the mark
C.east side of the mark
D.south side of the mark

单项选择题A buoy，being a shape of cylinder and with red group flashing，shows that it is（）.

A.left-side buoy
B.right-side buoy
C.a buoy of safety
D.a buoy of danger

单项选择题A buoy with a composite group-flashing light indicates a(n)（）.

A.anchorage area
B.fish net area
C.bifurcation
D.dredging area