单项选择题
A.电源功率 B.电源频率 C.电源相序 D.电源极性
A.电源电压 B.电源频率 C.电源相序 D.电压极性
A.20~40mm B.30~50mm C.60~80mm D.80~100mm
A.50mm B.70mm C.80mm D.100mm
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