明挖爆破时，起爆信号是()。A.鸣30s、停、鸣30s、停、鸣30sB.鸣20s、鸣10s、停、鸣20s、鸣10s、停、鸣20s、鸣10sC.鸣10s

1.[]明挖爆破时，起爆信号是( )。A.鸣30s、停、鸣30s、停、鸣30s B.鸣20s、鸣10s、停、鸣20s、鸣10s、停、鸣20s、鸣10s C.鸣10s、停、鸣10s、停、鸣10s D.鸣20s、停、鸣20s、停、鸣20sABCD