单项选择题
A.the system is manned manually
B.the system is situated remotely from the operator
C.the system is controlled automatically
D.all the above
单项选择题 Switchboards may be of the dead-front type in which all live parts are installed behind （） and only the operation handles and instruments are on the front.
单项选择题 The emergency generator or emergency battery is connected to（） on most large ships.
单项选择题 The main generators are connected to（）.