单选,5分] 经纬仪在盘左位置时将望远镜大致置平,使其竖盘读数在0°左右,望远镜物镜端抬高 时读数减少,其盘左的竖直角公式()
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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