【单选题】
根据《水利水电工程施工通用安全技术规程》,明挖爆破的预告信号是()。
A、间断鸣三次长声,即鸣30s、停、鸣30s、停、鸣30s
B、间断鸣一长、一短三次,即鸣20s、鸣10s、停、鸣20s、鸣10s、停、鸣20s、鸣10s
C、连续三短声,即鸣10s、停、鸣10s、停、鸣10s
D、一次长声,鸣60s
A、间断鸣三次长声,即鸣30s、停、鸣30s、停、鸣30s
B、间断鸣一长、一短三次,即鸣20s、鸣10s、停、鸣20s、鸣10s、停、鸣20s、鸣10s
C、连续三短声,即鸣10s、停、鸣10s、停、鸣10s
D、一次长声,鸣60s