第5题
A.Printed Circuit Board
B.Play Circuit Board
C.Printed Circuit Box
D.Play Circuit Box
第7题
第8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(环) at each end
C.gives no visual indication of having opened the circuit
D.trips to break the circuit and may be reset
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