Miss Zhang takes out of a piece of paper, draws a very small circle of half a centimeter semidiameter in red pen, and takes out a black pen.

• 你们看，这里有一张纸，上面有一个很小的红圈，你在离这张纸大约20厘米的地方用这支黑笔去点这个红圈，一定要点在圈内，看看你点的准不准？