A:
B:
C:
D:
A. Today is Sunday.
B. He flies a kite.
C. The girl plays with her teddy bear.
D. We read books.
E. They play catch with a ball.
如图所示,在水平桌面上用手指压铅笔尖,铅笔在竖直位置处于静止状态,在图中画出铅笔受到桌面的弹力的示意图。