A:how much did it cost
B:how much it cost
C:how much it costed
D:it cost how much
以下说法正确的是( )
is very important for us to learn English well.
如图甲所示,在粗糙水平面上,物体A在水平向右的外力F的作用下做直线运动,其速度﹣时间图象如图乙所示,下列判断正确的是( )