Before switching on gyro-compass,you should make sure that the power supply on board is ______.
A.high or low
B.AC or DC
C.strong or weak
D.on or off
正确答案是B
Before switching on gyro-compass,you should make sure that the power supply on board is ______.
A.high or low
B.AC or DC
C.strong or weak
D.on or off
正确答案是B