单项选择题
A circuit breaker differs from a fuse in that a circuit breaker （）.
A.melts and must be replaced B.is enclosed in a tube of insulating material with metal ferrules at each end C.gives no visual indication of having opened the circuit D.trips to break the circuit and may be reset
单项选择题 Voltage generated by most AC generators is fed from the machine to the bus by means of（）.
单项选择题 Electrical leads and insulation on a motor should be painted with（）.
单项选择题 The electrolyte in a lead-acid storage battery consists of distilled water and （）.
