Question

the definition of a circle uses the undefined term _______.
arc
line
plane
ray

Explanation:

Undefined terms in geometry include point, line, and plane. A circle is defined as the set of all points in a plane equidistant from a fixed center point. This definition relies on the undefined term "plane" to specify the 2-dimensional space where the circle exists; arc, line, and ray are defined terms or not required for the core definition of a circle.

Answer:

plane