塞尺测量时塞片之间应无（）等杂物。
参考答案：颗粒和油污
He______ and was made to repeat it.
A．didn'tunderstand
B．didn'tbeunderstood
C．wasn'tunderstand
D．wasn'tunderstood
电流互感器正常运行中，二次侧处于开路状态。（）
