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

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

单项选择题A ship under construction or major repair will acquire permanent magnetism due to（）while sitting stationary in the earth’s magnetic field.

A.hammering and jarring
B.vibration and pounding
C.varying magnetic fields
D.stable or permanent magnetism of the ship

单项选择题When changing from a compass course to a true course you should apply（）.

A.variation
B.deviation
C.variation and deviation
D.a correction for the direction of current set

单项选择题When adjusting a magnetic compass using the fore-and-aft permanent magnets，you should（）.

A.use the magnets one at a time，putting one in one side and then one on the opposite side，one step higher
B.use the magnets in pairs，starting at the top，with trays at the highest point of travel
C.use the magnets in pairs，from the bottom up，with the trays at the lowest point of travel
D.fill all the trays with magnets，then remove them one-by-one until the deviation is removed

单项选择题When adjusting a magnetic compass for error，a deviation table should be made（）.

A.before correcting for any deviation
B.after correcting for variation
C.after adjusting the fore-and-aft and athwartships permanent magnets
D.before the quadrantal correctors are placed on the compass