A:how ofte
B:how long
C:how far
D:how soo
我国现阶段最基本的国情是( )
两列简谐横波的振幅都是20cm,传播速度大小相同.实线波的频率为2Hz,沿x轴正方向传播,虚线波沿x轴负方向传播.某时刻两列波在如图所示区域相遇,则( )
— Do you want to be chess player when you grow up?
— Of course not. I play chess just for fun.