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、停、鸣10s、停、鸣10sD . 鸣20s、停、鸣20s、停、鸣20s
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