Variation in a compass is caused by（）.

A . If the quadrantal spheres are out as far as possible replace them with smaller spheres B . If the quadrantal spheres are in as far as possible remove one of the spheres C . If the quadrantal spheres are in as far as possible replace them with smaller spheres D . If the quadrantal spheres are out as far as possible，move the quadrantal spheres i

A . be shielded from direct sunlight B . be locked into a constant heading C . have any air bubbles replaced with nitrogen D . have the compensating magnets removed

A . zero B . equal to variation C . eliminated by adjusting the compass D . constant at any geographical locatio

A、deviation B、annual rate of variation change C、precession D、compass error

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 iro

A . Move the quadrantal spheres closer to the compass B . Raise the heeling magnet if the red end is up C . Remove some of the Flinders bar D . Raise or lower the athwartship magnet

A . the vessel's heading B . sea conditions C . seasons D . the vessel's positio

A . vessel's geographic position B . vessel's heading C . earth's magnetic field D . influence of the magnetic materials of the vessel

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 magnet

A . If the quadrantal spheres are all the way out，replace them with smaller spheres B . If the quadrantal spheres are all the way in，replace them with larger spheres C . If the quadrantal spheres are all of the way out，move the spheres in D . If the quadrantal spheres are all the way out，replace them with larger spheres.

A . polar regions B . horse latitudes C . roaring forties D . doldrum

A . Magnetic compass table B . Magnetic meridians C . Isogonic lines D . Variation is not indicated on small-scale nautical chart

A . Worn gears in the compass housing B . Magnetism from the earth's magnetic field C . Magnetism within the vessel D . Lack of oil in the compass bearing

A . nonmagnetic B . weatherproof C . corrosion resistant D . capable of being permanently affixed to the vessel

A . Compass error and variation are equal B . Compass north will be true north C . Variation will equal deviation D . There will be no compass error

A . Gray lines on the uppermost inset chart B . Red lines on the main body of the chart C . In parenthesis on the lines of equal magnetic variation D . Annual rate of change is not show

A . Card B . Needle C . Lubber's line D . Gimbal

A .  echo B .  jitter C .  packet loss D .  digitized sampling

A . placed in a fixed bracket when being used B . clamped to any position convenient for the coxswain to see it C . permanently mounted on the lifeboat's centerline D . mounted in the center of the boat to eliminate deviatio

A．Y B．N C．NG

此题为判断题(对，错)。

A．8.3% B．6.5% C．4.2% D．10.2%