浅孔爆破中, 为了避免爆后留有残埂或产生超挖, 炮孔深度需根据不同岩石情况可以大于、等于或小于开挖阶梯高度。 ( )
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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