单项选择题
A、辅助开关B、真空灭弧室C、波纹管D、操动机构
A.contradicted them by saying;makeB.countered by saying;make forC.opposed by saying;make upD.have been lagged behind;slip off
A、短路B、开路C、工作接地D、保护接地
A.正向导通区B.反向截止区C.反向击穿区D.放大区
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