太原刘晓晓同学问:世上有万能机器吗?一位小朋友独出心裁地发明出一台机器,说是万能的,上面装着铁锤、扫帚、木锯、钻头和铁锹……真是应有尽有了(图1)。这时,有人问他,如果用这台万能机器伐木,那么其他那些工具都干什么呢,不都闲起来了吗?小朋友被问得哑口无言。看来,伐木机就 The student of Taiyuan Liu Xiaoxiao asked: Is there a universal machine in the world? A child invented a machine ingeniously, saying that it is omnipotent with hammers, brooms, saws, drills, and shovels on it... it really deserves it (Figure 1). At this time, someone asked him, if you use this universal machine to log, what are you doing with all those other tools? You are not free. The child is left speechless. It seems that the logging machine