A:can ask, will waste
B:must have asked, had wasted
C:could have asked, was wasted
D:shouldn’t have asked, would be wasted
如图是某同学在做“测定匀加速直线运动的加速度”实验中的一条纸带,每相邻两个点中间还有四个点未画出.打点计时器接在频率为50赫兹的电源上.则打B点时小车的速度vB=____.m/s小车的加速度a=____m/s2.(结果保留三位有效数字)
—Certainly. In the principal's office. They ________ happily at that time.
潜水员在水底听不到地面上的声音。( )