Question

which undefined term is used to define an angle?○ line○ plane○ point○ ray

Explanation:

An angle is defined as the figure formed by two rays sharing a common endpoint. Rays are defined using the undefined term "point" (the endpoint) and "line", but the core undefined term that serves as the foundation for defining an angle is the point, since the angle's vertex is a point, and the rays originate from this point.

Answer:

point