开掘工作面放炮前后，要在附近()米的巷道内洒水灭尘。
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车削偏心工件时，应保证偏心的中心与机床主轴的回转中心重合。()
什么是欠定位？为什么不能采用欠定位？什么是过定位？
设计基准和定位基准重合时，不存在基准不重合误差。()
When running a large, low-speed, main propulsion diesel engine on heavy fuel, which of the
A. The diesel oil must never be allowed to mix with the heavy fuel
B. The temperature of the fuel from the pre–heater should be gradually reduced after switching over the three–way valve
C. The heating steam to the pre-heater should be secured as soon as the diesel fuel passes through the three-way valve
D. The heating steam must be secured before the diesel oil passes through the three-way valve
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