Which dress do you like, the blue one and the red one?
①电磁打点计时器和电火花计时器都是使用____(填“直流”或“交流”)电源的计时仪器.假如电源频率是40Hz时,它每隔____s打一个点.
②某同学利用打点计时器所记录的纸带来研究做匀变速直线运动小车的运动情况,实验中获得一条纸带,如下图,其中两相邻计数点间有四个点未画出.已知所用电源的频率为50Hz,则打A点时小车运动的速度vA=____m/s.(小数点后保留两位数字)
— It's not officially confirmed yet. The committee are _________ it over.