单项选择题
The MOST important feature of the material used for making the binnacle of a standard magnetic compass is that it is（）.
A.nonmagnetic B.weatherproof C.corrosion resistant D.capable of being permanently affixed to the vessel
单项选择题 The magnetic compass operates on the principle that（）.
单项选择题 The magnetic compass magnets are acted on by the horizontal component of the Earth’s total magnetic force. This magnetic force is GREATEST at the（）.
单项选择题 The lubber’s line on a magnetic compass indicates（）.
