矩形母线采用螺栓固定搭接时，连接处距支柱绝缘子的支持夹板边缘不应小于（）。
A.10mm
B.30mm
C.50mm
D.70mm
参考答案：C
Not until Mr. Smith came to China ___ what kind of a country she is.
A．did he know
B．he knew
C．he didn't know
D．he could know
流水步距的定义是：相邻专业队，相继投入不同施工段开始作业的时间间隔。 ( )
