子痫前期轻度患者应低蛋白、低盐饮食，但不严格限盐。
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开工稳定系统充瓦斯后，应采样分析氧含量不大于（）。
A. 10%
B. 30%
C. 50%
D. 90%
生产矿井延深水平，只有在建成新水平的防、排水系统后，方可开拓掘进。
A. 正确
B. 错误
The static suction lift of a pump is the difference in elevation between the （）.
A. centerline of the pump and the level of the liquid in the suction well when the source of liquid is below the pump
B. centerline of the pump and the suction liquid level when the source of liquid is above the pump
C. centerline of the pump and the level of the discharge liquid
D. liquid levels of the suction and discharge
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