高炉开炉送风后，炉前要保持铁口喷煤气状态，是否堵上铁口的标志是（）。
参考答案：铁口见渣流
--- “Where have you been?”
--- “I got caught in traffic; otherwise _____ sooner.”
A．I would be here
B．I have been here
C．I had been here
D．I would have been here
运行中的35kV的电压互感器二次回路，其电压降至少每（）年测试一次。
A.2
B.3
C.4
D.5
