—No, ____ ____.
一只猴子静止在悬挂于天花板的细棒上,现使悬挂棒的绳子断开,猴子和细棒一起向下运动,甲说此棒是静止的,乙说猴子是向下运动的,甲、乙两人所选的参考系分别是( )
一束光线垂直射向平面镜,反射角是 ____
His father takes him _____ school every day.