可以通过观察它旁边的指示灯即可。当AC开关被按下时，AC开关旁边的灯会亮起，代表此时为打开状态；当AC开关被按起时，AC开关旁边的灯会熄灭，代表此时为关闭状态。...

on/off 的用法(1) on 和 off 用于电器的开启或关闭 我们说: the light is on / put the light on / leave the light on etc. turn the light on/off or switch the light on/off Shall I leave the lights on or turn them off? ‘Is the heating on?’ ‘No, I switched it...