我国工程岩体分级标准中是根据哪些因素对岩石基本质量进行修正的?( )。①地应力大小; ②地下水; ③结构面方位; ④结构面粗糙度。
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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