质量为2 kg的物体静止在足够大的水平地面上，物体与地面间的动摩擦因数为0.2，最大静摩擦力与滑动摩擦力大小视为相等．从t＝0时刻开始，物体受到方向不变、大小呈周期性变化的水平拉力F的作用，F随时间t的变化规律如图3－2－7所示．重力加速度g取10 m/s2，则物体在t＝0至t＝12 s这段时间的位移大小为( )
图3－2－7
| A．18 m | B．54 m |
| C．72 m | D．198 m |
Thank you＿telling ＿＿about your day.
A.of; me B. for ;I C. for; me
What do you do?
A.I’m a teacher. B.I’m reading a book. C.I can cook dinner.
Can I ask you some questions?＿＿＿＿＿
A.Thank you B.Sure C. Great
＿＿do you go to bed? At 6:30.
A.When B.Who C.What
I get up ＿＿6:30,what about you? I usually get up＿＿7:00.
A.at;at B. at;at C.in;in