根据句意及汉语提示完成下列句子。

1. Franc is not a child at all. He can _______ _______ (照顾) himself well.

2. They do the work______ _______ _________(日日夜夜).

3. Children should sleep _______ _______ (至少) ten hours every day.

4. Our football team will _______ _______ (同……比赛) yours this Friday afternoon.

     Would you come and cheer them on?

5. To keep healthy, we should eat more fruit and vegetables ______ ______ (取代/代替) meat.

如图所示，一物体a以一定的初速度从粗糙水平面上的P点向固定的物体b运动，物体a在运动过程中所受到的摩擦阻力f与它距物体b的距离成正比．当物体a向右移动s时，速度减为零，那么物体a在从P点向右的位移为s/2时，a的动能为（　　）

A．小于初动能的一半

B．等于初动能的一半

C．大于初动能的一半

D．动能的减少量等于克服摩擦力做的功