—Oh, I only need ____orange juice.
A:some;a few
B:a few;some
C:a little;few
D:a little;a few
如图所示,斜面小车M静止在光滑水平面上,一边紧挨着墙壁.现再在斜面上加一物体m,且M、m相对静止,小车后来受力个数为( )