单选题The greatest directive force is exerted on the magnetic compass when the（）.A needles are nearly in line with the meridianB vessel is near the magnetic polesC variation is near zeroD vessel is near the magnetic equator

The force exerted by a propeller which tends to throw the stern right or left is called ______.

A.slip

B.sidewise force

C.rotational force

D.thrust

Which magnetic compass corrector（s）CANNOT be set on a heading of magnetic east or magnetic west ________．

A.Heeling magnet

B.Flinders bar

C.Fore-and-aft magnets

D.All of the above can be set on magnetic east or magnetic west headings

A.it

B.them

C.that

D.one

Reid vapor pressure is ______．

A.exerted by liquid cargo on the sides of a tank

B.exerted by liquid cargo on a cargo hose body

C.the lowest temperature and pressure that will cause a flammable liquid to give off vapors

D.a measurement of the amount of flammable vapors given off by a liquid at a certain temperature

Magnetic dip is a measurement of the angle between the ______.

A.geographic pole and the magnetic pole

B.lubber’s line and true north

C.horizontal and the magnetic line of force

D.compass heading and the magnetic heading

In Trial 9, the electrical force exerted by Sphere Y on Sphere X and the electrical force exerted by Sphere X on Sphere Y were exerted in which direction(s)?

A.east； east

B.east； west

C.west； west

D.west； east