气相色谱仪由气路单元、分析单元、检测器单元、温控单元和数据处理单元等组成
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汽包锅炉因水位低至极限水位而进行紧急停炉后应（）
A. 立即大量进水
B. 禁止进行补水
C. 可少量补水
D. 用“叫水法”判明缺水程度后再决定是否补水
Which two statements describe characteristics of IPv6 unicast addressing?（）
A. Global addresses start with 2000::/3.
B. Link-local addresses start with FE00:/12.
C. Link-local addresses start with FF00::/10.
D. There is only one loopback address and it is ::1.
E. If a global address is assigned to an interface, then that is the only allowable address for the interface.
两轴转向架中各型轮对的轮缘厚度段修限度不小于（）mm。
A. 31
B. 32
C. 33
D. 26
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