垂直角测量时,读数前应使____居中。
用光学经纬仪测量水平角与竖直角时,度盘与读数指标的关系是________。
You can _____ some bottles of wine, or some chocolates, or a bunch of flowers.
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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