单项选择题
At the master gyrocompass，the compass card is attached to the（）.
A.spider element B.sensitive element C.link arm D.pickup transformer
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（）.
单项选择题 To obtain accuracy in fixing by DF cross bearings，（）should be used.
