使用消弧绳断开空载线路，空载电流最大不宜超过（）A。
A.5
B.10
C.15
D.3
参考答案：D
They had been for many years.
A．lost touch with
B．out of touch
C．lost touch
D．out of touch with
一类环境中，钢筋混凝土梁的保护层厚度最小取（）。
A.15mm
C.25mm
B.20mm
D.30mm
