Answer: Undefined
Explanation:
In geometry there are three undefined terms that we use to define other terms:
- Point → In geometry a point has a location but no dimension.
- Plane → A plane extends is a 2-dimensional surface that extends infinitely on both sides.
- Line → A line is a one-dimensional undefined figure that extends infinitely in both the directions. It has length but has no width.
Hence, the correct option is "Undefined".