电磁波的波长是指[ ]
A．电磁波传播的距离
B．每秒内电磁波传播的距离
C．每振荡一次，电磁波传播的距离
D．每周期内，电磁波的距离
答案：C
人体触电的危险程度的决定因素是（）有关。
A、电流的大小；
B、电流的频率；
C、电流的相位；
D、触电的时间；
E、电流流过人体的部位；
My parents are always telling me to leave everything in the study_________.
A．as they were
B．as it was
C．like they were
D．like it was
