下列有关力的说法正确的是( )
A:重力就是万有引力
B:放在水平桌面上静止的物体所受弹力就是重力
C:滑动摩擦力总是阻碍物体运动的
D:力的作用是相互的
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A. The boy is going to the park.
B. Some newspapers are flying away.
C. The balloons are flying away.
D. These boys are playing football.
E. They are going to go to the park tomorrow.
样本频数分布反映了( )