一物体从长为L的光滑斜面的顶端由静止开始匀加速滑下，经时间t滑到底端，则下列说法正确的是( )

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A：物体运动到底端时的速度是 $\frac{L}{t}$

B：物体在 $\frac{t}{2}$ 时的即时速度是 $\frac{2 L}{t}$

C：物体运动到斜面中点时瞬时速度是 $\frac{\sqrt{2} L}{t}$

D：物体从顶点运动到斜面中点所需的时间是 $\frac{\sqrt{2} t}{4}$

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C

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根据首字母拼写单词，完成短文。

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