Question

which is a property of an angle?
has two sides that each extend forever in both directions
has two endpoints
has two center points
has two rays that share a common endpoint

Explanation:

An angle is formed by two rays that share a common endpoint. A ray extends infinitely in one direction, not both. An angle has one vertex (the common endpoint) not two endpoints or two center points.

Answer:

has two rays that share a common endpoint