单项选择题
A.turn off power first B.turn on power first C.with a test pen in hand D.tell C/E
While the parallel operation, （） must be used.A.ammeter...
单项选择题While the parallel operation, （） must be used.
A.ammeter B.voltmeter C.synchroscope D.A+B+C
When the bearing becomes dry from lack of oil, the moto...
单项选择题When the bearing becomes dry from lack of oil, the motor shaft may heat to （）an extent （） it welds itself to the bearing.
A.either；or B.neither；nor C.such；that D.so；that
An indicator on the main switchboard should show （） the...
单项选择题An indicator on the main switchboard should show （） the emergency battery is in service or not.
A.that B.when C.if D.whether
