要求S、P≤0.03%的钢是（）。
A.普通钢
B.优质钢
C.高级优质钢
参考答案：C
Was it at the school ______ was named after a hero _____ he spent his childhood?
A．which; that
B．where; where
C．that; where
D．which; where
电流互感器和电压互感器的缩写为（）。
A、CT；TV
B、TA；TV
C、CT；PT
D、TA；PT
