单项选择题
A compass card without north-seeking capability that is used for relative bearings is a(n)（）.
A.bearing circle B.pelorus C.bearing bar D.alidade
单项选择题 At the master gyrocompass，the compass card is attached to the（）.
单项选择题 Before switching on gyro-compass，you should make sure that the power supply on board is（）.
单项选择题 Calibration Stations give special transmissions for the calibration of ship’s（）.
