定短路持续时间（额定动稳定时间）
参考答案：
开关在合位置所能承载额定短时耐受电流的时间间隔。
Was it from Mary, _______ was working at a department store, ______ you learned the news?
A．who; who
B．that; which
C．who; that
D．who; which
钢尺量距、视距测量、光电测距等都是（）测量的方法之一。
A、曲线距离
B、斜线距离
C、直线距离
D、距离
