对轧管外表面氧化处理正确的是（）
A．调整氮气流量
B．调整二次冷却水喷水流量
C．检查更换密封条
D．打磨轧辊
参考答案：A, B, C
If the firefighters _____ in time, the fire would have resulted in many deaths in the hotel. [ ]
A. wouldn't have arrived
B. hadn't arrived
C. didn't arrive
D. shouldn't arrive
断路器失灵保护断开母联断路器的动作延时应整定为（）。
A、0.15s
B、0.3s
C、0.5s
