有一水垢在验算中不溶解，加热后缓慢溶解，有透明砂粒沉淀物，加入1%HF可有效溶解，其为()垢
A. 氧化镁
B. 硫酸盐
C. 碳酸盐
D. 硅酸盐
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操作记录应包括以下内容()。
A. 进出压力管道的介质的温度、压力、流量等
B. 介质的反应原理
C. 制定工艺流程的依据
D. 定期检验的质量
When a vessel navigates in an area with a small underkeel clearance but with adequate space to take avoiding action she ().
A. Should not be regarded as a vessel constrained by her draught
B. Should be regarded as a vessel constrained by her draught
C. Shall be regarded as a vessel restricted in her ability to maneuver
D. Should be regarded as a non-displacement vessel
按舵的支承分类有______。
A. 多支承舵
B. 双支承
C. 半悬挂舵和悬挂舵
D. A+B+C
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