单选题The permanent magnetism of a vessel may change in strength due to（）.A a collision with another vesselB being moored on a constant heading for a long period of timeC being struck by lightningD All of the above

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

What is used to correct for both induced and permanent magnetism，and consequently must be readjusted with radical changes in latitude ________．

A.Flinders bar

B.Soft iron spheres

C.Fore-and-aft permanent magnets in their trays

D.Heeling magnet

Permanent magnetism is found in ______.

A.hard iron

B.soft iron

C.vertical iron only

D.horizontal iron only

If a ship is proceeding towards the magnetic equator, the uncorrected deviation due to permanent magnetism ______.

A.increases

B.remains the same

C.decreases

D.is unimportant and may be neglected

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

A.They are not subject to permanent magnetism; no check is necessary

B.Semiannually

C.Annually

D.Every five years

This induced magnetism ______ the permanent magnetism already present in the ship．

A.will add to

B.will subtract from

C.may add to or subtract from

D.will not change

The magnetism in the various structures of a ship changing as a result of cruising，vibration，or aging is termed ______．

A.permanent magnetism

B.subpermanent magnetism

C.induced magnetism

D.variable magnetism

The permanent magnetism of a vessel may change in strength due to ______.

A.the nature of the cargo being carried

B.changes in heading

C.major structural repair

D.All of the above

A single vertical magnet placed underneath the compass in the binnacle is used to compensate for ______．

A.The horizontal component of the permanent magnetism

B.Deviation caused by the vessel's inclination from the vertical

C.Induced magnetism in the horizontal soft iron

D.Induced magnetism in the vertical soft iron

If your vessel is the stand-on vessel in a crossing situation ______.

A.you must keep your course and speed

B.you may change course and speed as the other vessel must keep clear

C.the other vessel must keep her course and speed

D.both vessels must keep their course and speed