.质量为m的物体以速度v0离开桌面，如图所示，当它经过A点时，所具有的机械能是（以桌面为参考平面，不计空气阻力）
A．
B．
C．
D．
答案：D
按要求进行句型转换。
1. You can see that is a pear.(改为否定疑问句)
_____________ _____________ see that is a pear?
2. I can give her my pencil. (改为同义句)
I can give my pencil _____________ _____________.
3. The boy behind the door is Tom. (对画线部分提问)
_____________ _____________ is Tom?
4. Li Lei is in Team Four. Lin Tao is in Team Four, too. (合为一句)
Li Lei and Lin Tao _____________ in _____________ same team.
5. Jack and Mike are American. (改为一般疑问句)
_____________ Jack and Mike _____________?
空中切变线和低涡是指出现在（）上的中低层天气系统。
A.850百帕或700百帕
B.500百帕
C.925百帕
D.400百帕
