A、21条
B、19条
C、25条
D、23条
A、A line is breadthless length.
B、A point is that which has no part.
C、A straight line is a line which lies evenly with the points on itself.
D、The ends of a line are points.
A、必需避免循环定义
B、必需给出要定义的事物的基本属性
C、必需使用学术的、晦涩的语言
D、必需避免太宽泛或太狭隘