题干
— Would you like to tell me ?
— Sure. Practice makes perfect.
A：how can I study English well
B：why do you learn English well
C：how I can study English well
D：why I learn English well
答案(点此获取答案解析）
C
的光滑斜面上，由底端向顶端做匀加速运动。当物体运动到斜面中点时，去掉推力，物体刚好能到达顶点，则推力的大小为（ ）