The Flinders bar and the quadrantal spheres should be tested for permanent magnetism at what interval（）.

单项选择题The Flinders bar on a magnetic compass compensates for the（）.

A.Induced magnetism in vertical soft iron
B.Induced magnetism in horizontal soft iron
C.Permanent magnetism in ship's steel
D.Vessel's inclination from the vertical

单项选择题In more recent years，（）has been used by civilians in many new ways to determine positions，such as in automobile and boat navigation，hiking，emergency rescue，and precision agriculture and mining.

A.GPS
B.GMDSS
C.AIS
D.Navtex

单项选择题By convention，the north seeking ends of a compass’ magnets are colored（）.

A.Black
B.Blue
C.Red
D.White

单项选择题Any piece of metal on becoming magnetized will develop regions of concentrated magnetism called（）.

A.flux
B.poles
C.magnets
D.azimuth

单项选择题A vessel is heading magnetic east and its magnetic compass indicates a heading of 086°.Which action should be taken to remove this error during compass adjustment（）.

A.If the blue ends of the magnets are aft，and the fore-and-aft tray is at the top，you should add some magnets
B.If the blue ends of the magnets are aft you should lower the fore-and-aft tray
C.If the blue ends of the magnets are aft，and the fore-and-aft tray is at the top，you should reverse the magnets
D.If the blue ends of the magnets are forward，and the fore-and-aft tray is at the bottom，you should add some magnets