单项选择题
The （） is a crystal which, under pressure, produces an electric current which varies with the pressure.
A.alternator B.glass thermometer C.burdon tube D.piezoelectric pressure transducer
单项选择题 Remote control means that （）.
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.
