单项选择题
A.铜质 B.铝质 C.钢质 D.镀锌钢质
A.20~30mm B.25~30mm C.30~40mm D.30~50mm
A.250V及以下 B.220V C.110V D.50V
A.0.2MΩB.0.5MΩC.1MΩD.2MΩ
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